diff --git a/NEWS b/NEWS
index 0b022cf8..490e89ed 100644
--- a/NEWS
+++ b/NEWS
@@ -4,6 +4,15 @@ GNU Bison NEWS
 
 ** Bug fixes
 
+*** Named %union support
+
+  Bison 3.0 introduced a regression on named %union such as
+
+    %union foo { int ival; };
+
+  The possibility to use a name was introduced ``for Yacc compatibility''.
+  It is however not required by POSIX Yacc, and its usefulness is not clear.
+
 *** %define api.value.type union with %defines
 
   The yacc.c and glr.c parsers were broken when %defines was used
diff --git a/THANKS b/THANKS
index b38affc6..095d3683 100644
--- a/THANKS
+++ b/THANKS
@@ -126,6 +126,7 @@ Sebastien Fricker         sebastien.fricker@gmail.com
 Sergei Steshenko          sergstesh@yahoo.com
 Shura                     debil_urod@ngs.ru
 Stefano Lattarini         stefano.lattarini@gmail.com
+Stephen Cameron           stephenmcameron@gmail.com
 Steve Murphy              murf@parsetree.com
 Sum Wu                    sum@geekhouse.org
 Théophile Ranquet         theophile.ranquet@gmail.com
@@ -133,6 +134,7 @@ Thiru Ramakrishnan        thiru.ramakrishnan@gmail.com
 Tim Josling               tej@melbpc.org.au
 Tim Landscheidt           tim@tim-landscheidt.de
 Tim Van Holder            tim.van.holder@pandora.be
+Tobias Frost              tobi@debian.org
 Tom Lane                  tgl@sss.pgh.pa.us
 Tom Tromey                tromey@cygnus.com
 Tommy Nordgren            tommy.nordgren@chello.se
diff --git a/data/bison.m4 b/data/bison.m4
index c416c6c2..da59baf5 100644
--- a/data/bison.m4
+++ b/data/bison.m4
@@ -1061,3 +1061,6 @@ b4_percent_define_ifdef([api.value.type],
                 [['%s' and '%s' cannot be used together]],
                 [%yacc],
                 [%define api.value.type "union"])])])])
+
+# api.value.union.name.
+b4_percent_define_check_kind([api.value.union.name], [keyword])
diff --git a/data/c++.m4 b/data/c++.m4
index ffbde266..7c0fd78e 100644
--- a/data/c++.m4
+++ b/data/c++.m4
@@ -17,6 +17,11 @@
 # You should have received a copy of the GNU General Public License
 # along with this program.  If not, see <http://www.gnu.org/licenses/>.
 
+# Sanity checks, before defaults installed by c.m4.
+b4_percent_define_ifdef([[api.value.union.name]],
+  [b4_complain_at(b4_percent_define_get_loc([[api.value.union.name]]),
+                  [named %union is invalid in C++])])
+
 m4_include(b4_pkgdatadir/[c.m4])
 
 # b4_comment(TEXT, [PREFIX])
diff --git a/data/c.m4 b/data/c.m4
index d56f8d76..738244d4 100644
--- a/data/c.m4
+++ b/data/c.m4
@@ -97,7 +97,8 @@ m4_define([b4_api_PREFIX],
 m4_define_default([b4_prefix], [b4_api_prefix])
 
 # If the %union is not named, its name is YYSTYPE.
-m4_define_default([b4_union_name], [b4_api_PREFIX[]STYPE])
+b4_percent_define_default([[api.value.union.name]],
+                          [b4_api_PREFIX[][STYPE]])
 
 
 ## ------------------------ ##
@@ -608,10 +609,9 @@ m4_copy_force([b4_symbol_value_union], [b4_symbol_value])
 ])
 
 
-# ---------------- #
-# api.value.type.  #
-# ---------------- #
-
+# -------------------------- #
+# api.value.type = variant.  #
+# -------------------------- #
 
 # b4_value_type_setup_variant
 # ---------------------------
@@ -686,11 +686,13 @@ typedef ]b4_percent_define_get([[api.value.type]])[ ]b4_api_PREFIX[STYPE;
 [m4_bmatch(b4_percent_define_get([[api.value.type]]),
 [union\|union-directive],
 [[#if ! defined ]b4_api_PREFIX[STYPE && ! defined ]b4_api_PREFIX[STYPE_IS_DECLARED
-typedef union ]b4_union_name[ ]b4_api_PREFIX[STYPE;
-union ]b4_union_name[
+]b4_percent_define_get_syncline([[api.value.union.name]])[
+union ]b4_percent_define_get([[api.value.union.name]])[
 {
 ]b4_user_union_members[
 };
+]b4_percent_define_get_syncline([[api.value.union.name]])[
+typedef union ]b4_percent_define_get([[api.value.union.name]])[ ]b4_api_PREFIX[STYPE;
 # define ]b4_api_PREFIX[STYPE_IS_TRIVIAL 1
 # define ]b4_api_PREFIX[STYPE_IS_DECLARED 1
 #endif
diff --git a/doc/bison.texi b/doc/bison.texi
index c3c9746f..11bd2d86 100644
--- a/doc/bison.texi
+++ b/doc/bison.texi
@@ -3851,7 +3851,7 @@ example:
 @noindent
 specifies the union tag @code{value}, so the corresponding C type is
 @code{union value}.  If you do not specify a tag, it defaults to
-@code{YYSTYPE}.
+@code{YYSTYPE} (@pxref{%define Summary,,api.value.union.name}).
 
 As another extension to POSIX, you may specify multiple @code{%union}
 declarations; their contents are concatenated.  However, only the first
@@ -6014,12 +6014,12 @@ Use this @var{type} as semantic value.
 @item Default Value:
 @itemize @minus
 @item
-@code{%union} if @code{%union} is used, otherwise @dots{}
+@code{union-directive} if @code{%union} is used, otherwise @dots{}
 @item
 @code{int} if type tags are used (i.e., @samp{%token <@var{type}>@dots{}} or
-@samp{%token <@var{type}>@dots{}} is used), otherwise @dots{}
+@samp{%type <@var{type}>@dots{}} is used), otherwise @dots{}
 @item
-@code{""}
+undefined.
 @end itemize
 
 @item History:
@@ -6030,6 +6030,30 @@ introduced in Bison 3.0.  Was introduced for Java only in 2.3b as
 @c api.value.type
 
 
+@c ================================================== api.value.union.name
+@deffn Directive {%define api.value.union.name} @var{name}
+@itemize @bullet
+@item Language(s):
+C
+
+@item Purpose:
+The tag of the generated @code{union} (@emph{not} the name of the
+@code{typedef}).  This variable is set to @code{@var{id}} when @samp{%union
+@var{id}} is used.  There is no clear reason to give this union a name.
+
+@item Accepted Values:
+Any valid identifier.
+
+@item Default Value:
+@code{YYSTYPE}.
+
+@item History:
+Introduced in Bison 3.0.3.
+@end itemize
+@end deffn
+@c api.value.type
+
+
 @c ================================================== location_type
 @deffn Directive {%define location_type}
 Obsoleted by @code{api.location.type} since Bison 2.7.
diff --git a/src/parse-gram.c b/src/parse-gram.c
index 9251b149..825e2b09 100644
--- a/src/parse-gram.c
+++ b/src/parse-gram.c
@@ -129,7 +129,7 @@ extern int gram_debug;
     param_parse  = 1 << 1,
     param_both   = param_lex | param_parse
   } param_type;
-#line 645 "src/parse-gram.y" /* yacc.c:355  */
+#line 647 "src/parse-gram.y" /* yacc.c:355  */
 #include "muscle-tab.h"
 
 #line 136 "src/parse-gram.c" /* yacc.c:355  */
@@ -200,7 +200,7 @@ extern int gram_debug;
 
 /* Value type.  */
 #if ! defined GRAM_STYPE && ! defined GRAM_STYPE_IS_DECLARED
-typedef union GRAM_STYPE GRAM_STYPE;
+
 union GRAM_STYPE
 {
 #line 182 "src/parse-gram.y" /* yacc.c:355  */
@@ -223,7 +223,7 @@ named_ref *named_ref;
 param_type param;
 #line 409 "src/parse-gram.y" /* yacc.c:355  */
 code_props_type code_type;
-#line 647 "src/parse-gram.y" /* yacc.c:355  */
+#line 649 "src/parse-gram.y" /* yacc.c:355  */
 
   struct
   {
@@ -233,6 +233,8 @@ code_props_type code_type;
 
 #line 235 "src/parse-gram.c" /* yacc.c:355  */
 };
+
+typedef union GRAM_STYPE GRAM_STYPE;
 # define GRAM_STYPE_IS_TRIVIAL 1
 # define GRAM_STYPE_IS_DECLARED 1
 #endif
@@ -259,7 +261,7 @@ int gram_parse (void);
 
 /* Copy the second part of user declarations.  */
 
-#line 263 "src/parse-gram.c" /* yacc.c:358  */
+#line 265 "src/parse-gram.c" /* yacc.c:358  */
 /* Unqualified %code blocks.  */
 #line 33 "src/parse-gram.y" /* yacc.c:359  */
 
@@ -335,7 +337,7 @@ int gram_parse (void);
   static void add_param (param_type type, char *decl, location loc);
   static param_type current_param = param_none;
 
-#line 339 "src/parse-gram.c" /* yacc.c:359  */
+#line 341 "src/parse-gram.c" /* yacc.c:359  */
 
 #ifdef short
 # undef short
@@ -621,14 +623,14 @@ static const yytype_uint16 yyrline[] =
      295,   300,   306,   307,   308,   309,   314,   319,   320,   321,
      322,   323,   324,   324,   325,   326,   350,   351,   352,   353,
      357,   358,   367,   368,   369,   373,   385,   389,   393,   401,
-     412,   413,   423,   424,   428,   440,   440,   445,   445,   450,
-     461,   476,   477,   478,   479,   483,   484,   489,   491,   496,
-     501,   511,   513,   518,   519,   523,   524,   528,   529,   530,
-     535,   540,   545,   551,   557,   568,   569,   578,   579,   585,
-     586,   587,   594,   594,   602,   603,   604,   609,   612,   614,
-     616,   618,   620,   622,   624,   629,   630,   640,   641,   666,
-     667,   668,   669,   681,   683,   692,   697,   698,   703,   711,
-     712
+     412,   413,   423,   424,   430,   442,   442,   447,   447,   452,
+     463,   478,   479,   480,   481,   485,   486,   491,   493,   498,
+     503,   513,   515,   520,   521,   525,   526,   530,   531,   532,
+     537,   542,   547,   553,   559,   570,   571,   580,   581,   587,
+     588,   589,   596,   596,   604,   605,   606,   611,   614,   616,
+     618,   620,   622,   624,   626,   631,   632,   642,   643,   668,
+     669,   670,   671,   683,   685,   694,   699,   700,   705,   713,
+     714
 };
 #endif
 
@@ -1002,73 +1004,73 @@ yy_symbol_value_print (FILE *yyoutput, int yytype, YYSTYPE const * const yyvalue
           case 3: /* "string"  */
 #line 188 "src/parse-gram.y" /* yacc.c:684  */
       { fputs (quotearg_style (c_quoting_style, ((*yyvaluep).code)), yyo); }
-#line 1006 "src/parse-gram.c" /* yacc.c:684  */
+#line 1008 "src/parse-gram.c" /* yacc.c:684  */
         break;
 
     case 23: /* "%<flag>"  */
 #line 196 "src/parse-gram.y" /* yacc.c:684  */
       { fprintf (yyo, "%%%s", ((*yyvaluep).uniqstr)); }
-#line 1012 "src/parse-gram.c" /* yacc.c:684  */
+#line 1014 "src/parse-gram.c" /* yacc.c:684  */
         break;
 
     case 39: /* "{...}"  */
 #line 189 "src/parse-gram.y" /* yacc.c:684  */
       { fprintf (yyo, "{\n%s\n}", ((*yyvaluep).code)); }
-#line 1018 "src/parse-gram.c" /* yacc.c:684  */
+#line 1020 "src/parse-gram.c" /* yacc.c:684  */
         break;
 
     case 40: /* "%?{...}"  */
 #line 189 "src/parse-gram.y" /* yacc.c:684  */
       { fprintf (yyo, "{\n%s\n}", ((*yyvaluep).code)); }
-#line 1024 "src/parse-gram.c" /* yacc.c:684  */
+#line 1026 "src/parse-gram.c" /* yacc.c:684  */
         break;
 
     case 41: /* "[identifier]"  */
 #line 194 "src/parse-gram.y" /* yacc.c:684  */
       { fprintf (yyo, "[%s]", ((*yyvaluep).uniqstr)); }
-#line 1030 "src/parse-gram.c" /* yacc.c:684  */
+#line 1032 "src/parse-gram.c" /* yacc.c:684  */
         break;
 
     case 42: /* "char"  */
 #line 184 "src/parse-gram.y" /* yacc.c:684  */
       { fputs (char_name (((*yyvaluep).character)), yyo); }
-#line 1036 "src/parse-gram.c" /* yacc.c:684  */
+#line 1038 "src/parse-gram.c" /* yacc.c:684  */
         break;
 
     case 43: /* "epilogue"  */
 #line 189 "src/parse-gram.y" /* yacc.c:684  */
       { fprintf (yyo, "{\n%s\n}", ((*yyvaluep).code)); }
-#line 1042 "src/parse-gram.c" /* yacc.c:684  */
+#line 1044 "src/parse-gram.c" /* yacc.c:684  */
         break;
 
     case 45: /* "identifier"  */
 #line 193 "src/parse-gram.y" /* yacc.c:684  */
       { fputs (((*yyvaluep).uniqstr), yyo); }
-#line 1048 "src/parse-gram.c" /* yacc.c:684  */
+#line 1050 "src/parse-gram.c" /* yacc.c:684  */
         break;
 
     case 46: /* "identifier:"  */
 #line 195 "src/parse-gram.y" /* yacc.c:684  */
       { fprintf (yyo, "%s:", ((*yyvaluep).uniqstr)); }
-#line 1054 "src/parse-gram.c" /* yacc.c:684  */
+#line 1056 "src/parse-gram.c" /* yacc.c:684  */
         break;
 
     case 49: /* "%{...%}"  */
 #line 189 "src/parse-gram.y" /* yacc.c:684  */
       { fprintf (yyo, "{\n%s\n}", ((*yyvaluep).code)); }
-#line 1060 "src/parse-gram.c" /* yacc.c:684  */
+#line 1062 "src/parse-gram.c" /* yacc.c:684  */
         break;
 
     case 51: /* "<tag>"  */
 #line 197 "src/parse-gram.y" /* yacc.c:684  */
       { fprintf (yyo, "<%s>", ((*yyvaluep).uniqstr)); }
-#line 1066 "src/parse-gram.c" /* yacc.c:684  */
+#line 1068 "src/parse-gram.c" /* yacc.c:684  */
         break;
 
     case 54: /* "integer"  */
 #line 201 "src/parse-gram.y" /* yacc.c:684  */
       { fprintf (yyo, "%d", ((*yyvaluep).integer)); }
-#line 1072 "src/parse-gram.c" /* yacc.c:684  */
+#line 1074 "src/parse-gram.c" /* yacc.c:684  */
         break;
 
     case 55: /* "%param"  */
@@ -1085,35 +1087,35 @@ yy_symbol_value_print (FILE *yyoutput, int yytype, YYSTYPE const * const yyvalue
       case param_none: aver (false); break;
     }
 }
-#line 1089 "src/parse-gram.c" /* yacc.c:684  */
+#line 1091 "src/parse-gram.c" /* yacc.c:684  */
         break;
 
     case 65: /* code_props_type  */
 #line 410 "src/parse-gram.y" /* yacc.c:684  */
       { fprintf (yyo, "%s", code_props_type_string (((*yyvaluep).code_type))); }
-#line 1095 "src/parse-gram.c" /* yacc.c:684  */
+#line 1097 "src/parse-gram.c" /* yacc.c:684  */
         break;
 
     case 74: /* symbol.prec  */
 #line 205 "src/parse-gram.y" /* yacc.c:684  */
       { fprintf (yyo, "%s", ((*yyvaluep).symbol)->tag); }
-#line 1101 "src/parse-gram.c" /* yacc.c:684  */
+#line 1103 "src/parse-gram.c" /* yacc.c:684  */
         break;
 
     case 78: /* tag  */
 #line 197 "src/parse-gram.y" /* yacc.c:684  */
       { fprintf (yyo, "<%s>", ((*yyvaluep).uniqstr)); }
-#line 1107 "src/parse-gram.c" /* yacc.c:684  */
+#line 1109 "src/parse-gram.c" /* yacc.c:684  */
         break;
 
     case 88: /* variable  */
 #line 193 "src/parse-gram.y" /* yacc.c:684  */
       { fputs (((*yyvaluep).uniqstr), yyo); }
-#line 1113 "src/parse-gram.c" /* yacc.c:684  */
+#line 1115 "src/parse-gram.c" /* yacc.c:684  */
         break;
 
     case 89: /* value  */
-#line 656 "src/parse-gram.y" /* yacc.c:684  */
+#line 658 "src/parse-gram.y" /* yacc.c:684  */
       {
   switch (((*yyvaluep).value).kind)
     {
@@ -1122,31 +1124,31 @@ yy_symbol_value_print (FILE *yyoutput, int yytype, YYSTYPE const * const yyvalue
     case muscle_string:  fprintf (yyo, "\"%s\"", ((*yyvaluep).value).chars); break;
     }
 }
-#line 1126 "src/parse-gram.c" /* yacc.c:684  */
+#line 1128 "src/parse-gram.c" /* yacc.c:684  */
         break;
 
     case 90: /* id  */
 #line 205 "src/parse-gram.y" /* yacc.c:684  */
       { fprintf (yyo, "%s", ((*yyvaluep).symbol)->tag); }
-#line 1132 "src/parse-gram.c" /* yacc.c:684  */
+#line 1134 "src/parse-gram.c" /* yacc.c:684  */
         break;
 
     case 91: /* id_colon  */
 #line 206 "src/parse-gram.y" /* yacc.c:684  */
       { fprintf (yyo, "%s:", ((*yyvaluep).symbol)->tag); }
-#line 1138 "src/parse-gram.c" /* yacc.c:684  */
+#line 1140 "src/parse-gram.c" /* yacc.c:684  */
         break;
 
     case 92: /* symbol  */
 #line 205 "src/parse-gram.y" /* yacc.c:684  */
       { fprintf (yyo, "%s", ((*yyvaluep).symbol)->tag); }
-#line 1144 "src/parse-gram.c" /* yacc.c:684  */
+#line 1146 "src/parse-gram.c" /* yacc.c:684  */
         break;
 
     case 93: /* string_as_id  */
 #line 205 "src/parse-gram.y" /* yacc.c:684  */
       { fprintf (yyo, "%s", ((*yyvaluep).symbol)->tag); }
-#line 1150 "src/parse-gram.c" /* yacc.c:684  */
+#line 1152 "src/parse-gram.c" /* yacc.c:684  */
         break;
 
 
@@ -1848,7 +1850,7 @@ YYLTYPE yylloc = yyloc_default;
   boundary_set (&yylloc.end, current_file, 1, 1);
 }
 
-#line 1852 "src/parse-gram.c" /* yacc.c:1429  */
+#line 1854 "src/parse-gram.c" /* yacc.c:1429  */
   yylsp[0] = yylloc;
   goto yysetstate;
 
@@ -2048,7 +2050,7 @@ yyreduce:
                         translate_code ((yyvsp[0].code), (yylsp[0]), true), (yylsp[0]));
       code_scanner_last_string_free ();
     }
-#line 2052 "src/parse-gram.c" /* yacc.c:1646  */
+#line 2054 "src/parse-gram.c" /* yacc.c:1646  */
     break;
 
   case 7:
@@ -2056,7 +2058,7 @@ yyreduce:
     {
       muscle_percent_define_ensure ((yyvsp[0].uniqstr), (yylsp[0]), true);
     }
-#line 2060 "src/parse-gram.c" /* yacc.c:1646  */
+#line 2062 "src/parse-gram.c" /* yacc.c:1646  */
     break;
 
   case 8:
@@ -2065,13 +2067,13 @@ yyreduce:
       muscle_percent_define_insert ((yyvsp[-1].uniqstr), (yylsp[-1]), (yyvsp[0].value).kind, (yyvsp[0].value).chars,
                                     MUSCLE_PERCENT_DEFINE_GRAMMAR_FILE);
     }
-#line 2069 "src/parse-gram.c" /* yacc.c:1646  */
+#line 2071 "src/parse-gram.c" /* yacc.c:1646  */
     break;
 
   case 9:
 #line 294 "src/parse-gram.y" /* yacc.c:1646  */
     { defines_flag = true; }
-#line 2075 "src/parse-gram.c" /* yacc.c:1646  */
+#line 2077 "src/parse-gram.c" /* yacc.c:1646  */
     break;
 
   case 10:
@@ -2080,7 +2082,7 @@ yyreduce:
       defines_flag = true;
       spec_defines_file = xstrdup ((yyvsp[0].code));
     }
-#line 2084 "src/parse-gram.c" /* yacc.c:1646  */
+#line 2086 "src/parse-gram.c" /* yacc.c:1646  */
     break;
 
   case 11:
@@ -2090,25 +2092,25 @@ yyreduce:
                                     "verbose",
                                     MUSCLE_PERCENT_DEFINE_GRAMMAR_FILE);
     }
-#line 2094 "src/parse-gram.c" /* yacc.c:1646  */
+#line 2096 "src/parse-gram.c" /* yacc.c:1646  */
     break;
 
   case 12:
 #line 306 "src/parse-gram.y" /* yacc.c:1646  */
     { expected_sr_conflicts = (yyvsp[0].integer); }
-#line 2100 "src/parse-gram.c" /* yacc.c:1646  */
+#line 2102 "src/parse-gram.c" /* yacc.c:1646  */
     break;
 
   case 13:
 #line 307 "src/parse-gram.y" /* yacc.c:1646  */
     { expected_rr_conflicts = (yyvsp[0].integer); }
-#line 2106 "src/parse-gram.c" /* yacc.c:1646  */
+#line 2108 "src/parse-gram.c" /* yacc.c:1646  */
     break;
 
   case 14:
 #line 308 "src/parse-gram.y" /* yacc.c:1646  */
     { spec_file_prefix = (yyvsp[0].code); }
-#line 2112 "src/parse-gram.c" /* yacc.c:1646  */
+#line 2114 "src/parse-gram.c" /* yacc.c:1646  */
     break;
 
   case 15:
@@ -2117,7 +2119,7 @@ yyreduce:
       nondeterministic_parser = true;
       glr_parser = true;
     }
-#line 2121 "src/parse-gram.c" /* yacc.c:1646  */
+#line 2123 "src/parse-gram.c" /* yacc.c:1646  */
     break;
 
   case 16:
@@ -2126,55 +2128,55 @@ yyreduce:
       muscle_code_grow ("initial_action", translate_code ((yyvsp[0].code), (yylsp[0]), false), (yylsp[0]));
       code_scanner_last_string_free ();
     }
-#line 2130 "src/parse-gram.c" /* yacc.c:1646  */
+#line 2132 "src/parse-gram.c" /* yacc.c:1646  */
     break;
 
   case 17:
 #line 319 "src/parse-gram.y" /* yacc.c:1646  */
     { language_argmatch ((yyvsp[0].code), grammar_prio, (yylsp[-1])); }
-#line 2136 "src/parse-gram.c" /* yacc.c:1646  */
+#line 2138 "src/parse-gram.c" /* yacc.c:1646  */
     break;
 
   case 18:
 #line 320 "src/parse-gram.y" /* yacc.c:1646  */
     { spec_name_prefix = (yyvsp[0].code); }
-#line 2142 "src/parse-gram.c" /* yacc.c:1646  */
+#line 2144 "src/parse-gram.c" /* yacc.c:1646  */
     break;
 
   case 19:
 #line 321 "src/parse-gram.y" /* yacc.c:1646  */
     { no_lines_flag = true; }
-#line 2148 "src/parse-gram.c" /* yacc.c:1646  */
+#line 2150 "src/parse-gram.c" /* yacc.c:1646  */
     break;
 
   case 20:
 #line 322 "src/parse-gram.y" /* yacc.c:1646  */
     { nondeterministic_parser = true; }
-#line 2154 "src/parse-gram.c" /* yacc.c:1646  */
+#line 2156 "src/parse-gram.c" /* yacc.c:1646  */
     break;
 
   case 21:
 #line 323 "src/parse-gram.y" /* yacc.c:1646  */
     { spec_outfile = (yyvsp[0].code); }
-#line 2160 "src/parse-gram.c" /* yacc.c:1646  */
+#line 2162 "src/parse-gram.c" /* yacc.c:1646  */
     break;
 
   case 22:
 #line 324 "src/parse-gram.y" /* yacc.c:1646  */
     { current_param = (yyvsp[0].param); }
-#line 2166 "src/parse-gram.c" /* yacc.c:1646  */
+#line 2168 "src/parse-gram.c" /* yacc.c:1646  */
     break;
 
   case 23:
 #line 324 "src/parse-gram.y" /* yacc.c:1646  */
     { current_param = param_none; }
-#line 2172 "src/parse-gram.c" /* yacc.c:1646  */
+#line 2174 "src/parse-gram.c" /* yacc.c:1646  */
     break;
 
   case 24:
 #line 325 "src/parse-gram.y" /* yacc.c:1646  */
     { version_check (&(yylsp[0]), (yyvsp[0].code)); }
-#line 2178 "src/parse-gram.c" /* yacc.c:1646  */
+#line 2180 "src/parse-gram.c" /* yacc.c:1646  */
     break;
 
   case 25:
@@ -2202,37 +2204,37 @@ yyreduce:
         }
       skeleton_arg (skeleton_user, grammar_prio, (yylsp[-1]));
     }
-#line 2206 "src/parse-gram.c" /* yacc.c:1646  */
+#line 2208 "src/parse-gram.c" /* yacc.c:1646  */
     break;
 
   case 26:
 #line 350 "src/parse-gram.y" /* yacc.c:1646  */
     { token_table_flag = true; }
-#line 2212 "src/parse-gram.c" /* yacc.c:1646  */
+#line 2214 "src/parse-gram.c" /* yacc.c:1646  */
     break;
 
   case 27:
 #line 351 "src/parse-gram.y" /* yacc.c:1646  */
     { report_flag |= report_states; }
-#line 2218 "src/parse-gram.c" /* yacc.c:1646  */
+#line 2220 "src/parse-gram.c" /* yacc.c:1646  */
     break;
 
   case 28:
 #line 352 "src/parse-gram.y" /* yacc.c:1646  */
     { yacc_flag = true; }
-#line 2224 "src/parse-gram.c" /* yacc.c:1646  */
+#line 2226 "src/parse-gram.c" /* yacc.c:1646  */
     break;
 
   case 30:
 #line 357 "src/parse-gram.y" /* yacc.c:1646  */
     { add_param (current_param, (yyvsp[0].code), (yylsp[0])); }
-#line 2230 "src/parse-gram.c" /* yacc.c:1646  */
+#line 2232 "src/parse-gram.c" /* yacc.c:1646  */
     break;
 
   case 31:
 #line 358 "src/parse-gram.y" /* yacc.c:1646  */
     { add_param (current_param, (yyvsp[0].code), (yylsp[0])); }
-#line 2236 "src/parse-gram.c" /* yacc.c:1646  */
+#line 2238 "src/parse-gram.c" /* yacc.c:1646  */
     break;
 
   case 34:
@@ -2240,7 +2242,7 @@ yyreduce:
     {
       grammar_start_symbol_set ((yyvsp[0].symbol), (yylsp[0]));
     }
-#line 2244 "src/parse-gram.c" /* yacc.c:1646  */
+#line 2246 "src/parse-gram.c" /* yacc.c:1646  */
     break;
 
   case 35:
@@ -2256,7 +2258,7 @@ yyreduce:
         symbol_list_free ((yyvsp[0].list));
       }
     }
-#line 2260 "src/parse-gram.c" /* yacc.c:1646  */
+#line 2262 "src/parse-gram.c" /* yacc.c:1646  */
     break;
 
   case 36:
@@ -2264,7 +2266,7 @@ yyreduce:
     {
       default_prec = true;
     }
-#line 2268 "src/parse-gram.c" /* yacc.c:1646  */
+#line 2270 "src/parse-gram.c" /* yacc.c:1646  */
     break;
 
   case 37:
@@ -2272,7 +2274,7 @@ yyreduce:
     {
       default_prec = false;
     }
-#line 2276 "src/parse-gram.c" /* yacc.c:1646  */
+#line 2278 "src/parse-gram.c" /* yacc.c:1646  */
     break;
 
   case 38:
@@ -2284,7 +2286,7 @@ yyreduce:
                         translate_code_braceless ((yyvsp[0].code), (yylsp[0])), (yylsp[0]));
       code_scanner_last_string_free ();
     }
-#line 2288 "src/parse-gram.c" /* yacc.c:1646  */
+#line 2290 "src/parse-gram.c" /* yacc.c:1646  */
     break;
 
   case 39:
@@ -2293,75 +2295,77 @@ yyreduce:
       muscle_percent_code_grow ((yyvsp[-1].uniqstr), (yylsp[-1]), translate_code_braceless ((yyvsp[0].code), (yylsp[0])), (yylsp[0]));
       code_scanner_last_string_free ();
     }
-#line 2297 "src/parse-gram.c" /* yacc.c:1646  */
+#line 2299 "src/parse-gram.c" /* yacc.c:1646  */
     break;
 
   case 40:
 #line 412 "src/parse-gram.y" /* yacc.c:1646  */
     { (yyval.code_type) = destructor; }
-#line 2303 "src/parse-gram.c" /* yacc.c:1646  */
+#line 2305 "src/parse-gram.c" /* yacc.c:1646  */
     break;
 
   case 41:
 #line 413 "src/parse-gram.y" /* yacc.c:1646  */
     { (yyval.code_type) = printer; }
-#line 2309 "src/parse-gram.c" /* yacc.c:1646  */
+#line 2311 "src/parse-gram.c" /* yacc.c:1646  */
     break;
 
   case 42:
 #line 423 "src/parse-gram.y" /* yacc.c:1646  */
     {}
-#line 2315 "src/parse-gram.c" /* yacc.c:1646  */
+#line 2317 "src/parse-gram.c" /* yacc.c:1646  */
     break;
 
   case 43:
 #line 424 "src/parse-gram.y" /* yacc.c:1646  */
-    { muscle_code_grow ("union_name", (yyvsp[0].uniqstr), (yylsp[0])); }
-#line 2321 "src/parse-gram.c" /* yacc.c:1646  */
+    { muscle_percent_define_insert ("api.value.union.name",
+                                         (yylsp[0]), muscle_keyword, (yyvsp[0].uniqstr),
+                                         MUSCLE_PERCENT_DEFINE_GRAMMAR_FILE); }
+#line 2325 "src/parse-gram.c" /* yacc.c:1646  */
     break;
 
   case 44:
-#line 429 "src/parse-gram.y" /* yacc.c:1646  */
+#line 431 "src/parse-gram.y" /* yacc.c:1646  */
     {
       union_seen = true;
       muscle_code_grow ("union_members", translate_code_braceless ((yyvsp[0].code), (yylsp[0])), (yylsp[0]));
       code_scanner_last_string_free ();
     }
-#line 2331 "src/parse-gram.c" /* yacc.c:1646  */
+#line 2335 "src/parse-gram.c" /* yacc.c:1646  */
     break;
 
   case 45:
-#line 440 "src/parse-gram.y" /* yacc.c:1646  */
+#line 442 "src/parse-gram.y" /* yacc.c:1646  */
     { current_class = nterm_sym; }
-#line 2337 "src/parse-gram.c" /* yacc.c:1646  */
+#line 2341 "src/parse-gram.c" /* yacc.c:1646  */
     break;
 
   case 46:
-#line 441 "src/parse-gram.y" /* yacc.c:1646  */
+#line 443 "src/parse-gram.y" /* yacc.c:1646  */
     {
       current_class = unknown_sym;
       current_type = NULL;
     }
-#line 2346 "src/parse-gram.c" /* yacc.c:1646  */
+#line 2350 "src/parse-gram.c" /* yacc.c:1646  */
     break;
 
   case 47:
-#line 445 "src/parse-gram.y" /* yacc.c:1646  */
+#line 447 "src/parse-gram.y" /* yacc.c:1646  */
     { current_class = token_sym; }
-#line 2352 "src/parse-gram.c" /* yacc.c:1646  */
+#line 2356 "src/parse-gram.c" /* yacc.c:1646  */
     break;
 
   case 48:
-#line 446 "src/parse-gram.y" /* yacc.c:1646  */
+#line 448 "src/parse-gram.y" /* yacc.c:1646  */
     {
       current_class = unknown_sym;
       current_type = NULL;
     }
-#line 2361 "src/parse-gram.c" /* yacc.c:1646  */
+#line 2365 "src/parse-gram.c" /* yacc.c:1646  */
     break;
 
   case 49:
-#line 451 "src/parse-gram.y" /* yacc.c:1646  */
+#line 453 "src/parse-gram.y" /* yacc.c:1646  */
     {
       symbol_list *list;
       tag_seen = true;
@@ -2369,11 +2373,11 @@ yyreduce:
         symbol_type_set (list->content.sym, (yyvsp[-1].uniqstr), (yylsp[-1]));
       symbol_list_free ((yyvsp[0].list));
     }
-#line 2373 "src/parse-gram.c" /* yacc.c:1646  */
+#line 2377 "src/parse-gram.c" /* yacc.c:1646  */
     break;
 
   case 50:
-#line 462 "src/parse-gram.y" /* yacc.c:1646  */
+#line 464 "src/parse-gram.y" /* yacc.c:1646  */
     {
       symbol_list *list;
       ++current_prec;
@@ -2385,341 +2389,341 @@ yyreduce:
       symbol_list_free ((yyvsp[0].list));
       current_type = NULL;
     }
-#line 2389 "src/parse-gram.c" /* yacc.c:1646  */
+#line 2393 "src/parse-gram.c" /* yacc.c:1646  */
     break;
 
   case 51:
-#line 476 "src/parse-gram.y" /* yacc.c:1646  */
+#line 478 "src/parse-gram.y" /* yacc.c:1646  */
     { (yyval.assoc) = left_assoc; }
-#line 2395 "src/parse-gram.c" /* yacc.c:1646  */
+#line 2399 "src/parse-gram.c" /* yacc.c:1646  */
     break;
 
   case 52:
-#line 477 "src/parse-gram.y" /* yacc.c:1646  */
+#line 479 "src/parse-gram.y" /* yacc.c:1646  */
     { (yyval.assoc) = right_assoc; }
-#line 2401 "src/parse-gram.c" /* yacc.c:1646  */
+#line 2405 "src/parse-gram.c" /* yacc.c:1646  */
     break;
 
   case 53:
-#line 478 "src/parse-gram.y" /* yacc.c:1646  */
+#line 480 "src/parse-gram.y" /* yacc.c:1646  */
     { (yyval.assoc) = non_assoc; }
-#line 2407 "src/parse-gram.c" /* yacc.c:1646  */
+#line 2411 "src/parse-gram.c" /* yacc.c:1646  */
     break;
 
   case 54:
-#line 479 "src/parse-gram.y" /* yacc.c:1646  */
+#line 481 "src/parse-gram.y" /* yacc.c:1646  */
     { (yyval.assoc) = precedence_assoc; }
-#line 2413 "src/parse-gram.c" /* yacc.c:1646  */
+#line 2417 "src/parse-gram.c" /* yacc.c:1646  */
     break;
 
   case 55:
-#line 483 "src/parse-gram.y" /* yacc.c:1646  */
+#line 485 "src/parse-gram.y" /* yacc.c:1646  */
     { current_type = NULL; }
-#line 2419 "src/parse-gram.c" /* yacc.c:1646  */
+#line 2423 "src/parse-gram.c" /* yacc.c:1646  */
     break;
 
   case 56:
-#line 484 "src/parse-gram.y" /* yacc.c:1646  */
+#line 486 "src/parse-gram.y" /* yacc.c:1646  */
     { current_type = (yyvsp[0].uniqstr); tag_seen = true; }
-#line 2425 "src/parse-gram.c" /* yacc.c:1646  */
+#line 2429 "src/parse-gram.c" /* yacc.c:1646  */
     break;
 
   case 57:
-#line 490 "src/parse-gram.y" /* yacc.c:1646  */
+#line 492 "src/parse-gram.y" /* yacc.c:1646  */
     { (yyval.list) = symbol_list_sym_new ((yyvsp[0].symbol), (yylsp[0])); }
-#line 2431 "src/parse-gram.c" /* yacc.c:1646  */
+#line 2435 "src/parse-gram.c" /* yacc.c:1646  */
     break;
 
   case 58:
-#line 492 "src/parse-gram.y" /* yacc.c:1646  */
+#line 494 "src/parse-gram.y" /* yacc.c:1646  */
     { (yyval.list) = symbol_list_append ((yyvsp[-1].list), symbol_list_sym_new ((yyvsp[0].symbol), (yylsp[0]))); }
-#line 2437 "src/parse-gram.c" /* yacc.c:1646  */
+#line 2441 "src/parse-gram.c" /* yacc.c:1646  */
     break;
 
   case 59:
-#line 497 "src/parse-gram.y" /* yacc.c:1646  */
+#line 499 "src/parse-gram.y" /* yacc.c:1646  */
     {
       (yyval.symbol) = (yyvsp[0].symbol);
       symbol_class_set ((yyvsp[0].symbol), token_sym, (yylsp[0]), false);
     }
-#line 2446 "src/parse-gram.c" /* yacc.c:1646  */
+#line 2450 "src/parse-gram.c" /* yacc.c:1646  */
     break;
 
   case 60:
-#line 502 "src/parse-gram.y" /* yacc.c:1646  */
+#line 504 "src/parse-gram.y" /* yacc.c:1646  */
     {
       (yyval.symbol) = (yyvsp[-1].symbol);
       symbol_user_token_number_set ((yyvsp[-1].symbol), (yyvsp[0].integer), (yylsp[0]));
       symbol_class_set ((yyvsp[-1].symbol), token_sym, (yylsp[-1]), false);
     }
-#line 2456 "src/parse-gram.c" /* yacc.c:1646  */
+#line 2460 "src/parse-gram.c" /* yacc.c:1646  */
     break;
 
   case 61:
-#line 512 "src/parse-gram.y" /* yacc.c:1646  */
+#line 514 "src/parse-gram.y" /* yacc.c:1646  */
     { (yyval.list) = symbol_list_sym_new ((yyvsp[0].symbol), (yylsp[0])); }
-#line 2462 "src/parse-gram.c" /* yacc.c:1646  */
+#line 2466 "src/parse-gram.c" /* yacc.c:1646  */
     break;
 
   case 62:
-#line 514 "src/parse-gram.y" /* yacc.c:1646  */
+#line 516 "src/parse-gram.y" /* yacc.c:1646  */
     { (yyval.list) = symbol_list_append ((yyvsp[-1].list), symbol_list_sym_new ((yyvsp[0].symbol), (yylsp[0]))); }
-#line 2468 "src/parse-gram.c" /* yacc.c:1646  */
+#line 2472 "src/parse-gram.c" /* yacc.c:1646  */
     break;
 
   case 63:
-#line 518 "src/parse-gram.y" /* yacc.c:1646  */
+#line 520 "src/parse-gram.y" /* yacc.c:1646  */
     { (yyval.list) = (yyvsp[0].list); }
-#line 2474 "src/parse-gram.c" /* yacc.c:1646  */
+#line 2478 "src/parse-gram.c" /* yacc.c:1646  */
     break;
 
   case 64:
-#line 519 "src/parse-gram.y" /* yacc.c:1646  */
+#line 521 "src/parse-gram.y" /* yacc.c:1646  */
     { (yyval.list) = symbol_list_append ((yyvsp[-1].list), (yyvsp[0].list)); }
-#line 2480 "src/parse-gram.c" /* yacc.c:1646  */
+#line 2484 "src/parse-gram.c" /* yacc.c:1646  */
     break;
 
   case 65:
-#line 523 "src/parse-gram.y" /* yacc.c:1646  */
+#line 525 "src/parse-gram.y" /* yacc.c:1646  */
     { (yyval.list) = symbol_list_sym_new ((yyvsp[0].symbol), (yylsp[0])); }
-#line 2486 "src/parse-gram.c" /* yacc.c:1646  */
+#line 2490 "src/parse-gram.c" /* yacc.c:1646  */
     break;
 
   case 66:
-#line 524 "src/parse-gram.y" /* yacc.c:1646  */
+#line 526 "src/parse-gram.y" /* yacc.c:1646  */
     { (yyval.list) = symbol_list_type_new ((yyvsp[0].uniqstr), (yylsp[0])); }
-#line 2492 "src/parse-gram.c" /* yacc.c:1646  */
+#line 2496 "src/parse-gram.c" /* yacc.c:1646  */
     break;
 
   case 68:
-#line 529 "src/parse-gram.y" /* yacc.c:1646  */
+#line 531 "src/parse-gram.y" /* yacc.c:1646  */
     { (yyval.uniqstr) = uniqstr_new ("*"); }
-#line 2498 "src/parse-gram.c" /* yacc.c:1646  */
+#line 2502 "src/parse-gram.c" /* yacc.c:1646  */
     break;
 
   case 69:
-#line 530 "src/parse-gram.y" /* yacc.c:1646  */
+#line 532 "src/parse-gram.y" /* yacc.c:1646  */
     { (yyval.uniqstr) = uniqstr_new (""); }
-#line 2504 "src/parse-gram.c" /* yacc.c:1646  */
+#line 2508 "src/parse-gram.c" /* yacc.c:1646  */
     break;
 
   case 70:
-#line 536 "src/parse-gram.y" /* yacc.c:1646  */
+#line 538 "src/parse-gram.y" /* yacc.c:1646  */
     {
       current_type = (yyvsp[0].uniqstr);
       tag_seen = true;
     }
-#line 2513 "src/parse-gram.c" /* yacc.c:1646  */
+#line 2517 "src/parse-gram.c" /* yacc.c:1646  */
     break;
 
   case 71:
-#line 541 "src/parse-gram.y" /* yacc.c:1646  */
+#line 543 "src/parse-gram.y" /* yacc.c:1646  */
     {
       symbol_class_set ((yyvsp[0].symbol), current_class, (yylsp[0]), true);
       symbol_type_set ((yyvsp[0].symbol), current_type, (yylsp[0]));
     }
-#line 2522 "src/parse-gram.c" /* yacc.c:1646  */
+#line 2526 "src/parse-gram.c" /* yacc.c:1646  */
     break;
 
   case 72:
-#line 546 "src/parse-gram.y" /* yacc.c:1646  */
+#line 548 "src/parse-gram.y" /* yacc.c:1646  */
     {
       symbol_class_set ((yyvsp[-1].symbol), current_class, (yylsp[-1]), true);
       symbol_type_set ((yyvsp[-1].symbol), current_type, (yylsp[-1]));
       symbol_user_token_number_set ((yyvsp[-1].symbol), (yyvsp[0].integer), (yylsp[0]));
     }
-#line 2532 "src/parse-gram.c" /* yacc.c:1646  */
+#line 2536 "src/parse-gram.c" /* yacc.c:1646  */
     break;
 
   case 73:
-#line 552 "src/parse-gram.y" /* yacc.c:1646  */
+#line 554 "src/parse-gram.y" /* yacc.c:1646  */
     {
       symbol_class_set ((yyvsp[-1].symbol), current_class, (yylsp[-1]), true);
       symbol_type_set ((yyvsp[-1].symbol), current_type, (yylsp[-1]));
       symbol_make_alias ((yyvsp[-1].symbol), (yyvsp[0].symbol), (yyloc));
     }
-#line 2542 "src/parse-gram.c" /* yacc.c:1646  */
+#line 2546 "src/parse-gram.c" /* yacc.c:1646  */
     break;
 
   case 74:
-#line 558 "src/parse-gram.y" /* yacc.c:1646  */
+#line 560 "src/parse-gram.y" /* yacc.c:1646  */
     {
       symbol_class_set ((yyvsp[-2].symbol), current_class, (yylsp[-2]), true);
       symbol_type_set ((yyvsp[-2].symbol), current_type, (yylsp[-2]));
       symbol_user_token_number_set ((yyvsp[-2].symbol), (yyvsp[-1].integer), (yylsp[-1]));
       symbol_make_alias ((yyvsp[-2].symbol), (yyvsp[0].symbol), (yyloc));
     }
-#line 2553 "src/parse-gram.c" /* yacc.c:1646  */
+#line 2557 "src/parse-gram.c" /* yacc.c:1646  */
     break;
 
   case 81:
-#line 588 "src/parse-gram.y" /* yacc.c:1646  */
+#line 590 "src/parse-gram.y" /* yacc.c:1646  */
     {
       yyerrok;
     }
-#line 2561 "src/parse-gram.c" /* yacc.c:1646  */
+#line 2565 "src/parse-gram.c" /* yacc.c:1646  */
     break;
 
   case 82:
-#line 594 "src/parse-gram.y" /* yacc.c:1646  */
+#line 596 "src/parse-gram.y" /* yacc.c:1646  */
     { current_lhs ((yyvsp[-1].symbol), (yylsp[-1]), (yyvsp[0].named_ref)); }
-#line 2567 "src/parse-gram.c" /* yacc.c:1646  */
+#line 2571 "src/parse-gram.c" /* yacc.c:1646  */
     break;
 
   case 83:
-#line 595 "src/parse-gram.y" /* yacc.c:1646  */
+#line 597 "src/parse-gram.y" /* yacc.c:1646  */
     {
     /* Free the current lhs. */
     current_lhs (0, (yylsp[-3]), 0);
   }
-#line 2576 "src/parse-gram.c" /* yacc.c:1646  */
+#line 2580 "src/parse-gram.c" /* yacc.c:1646  */
     break;
 
   case 84:
-#line 602 "src/parse-gram.y" /* yacc.c:1646  */
+#line 604 "src/parse-gram.y" /* yacc.c:1646  */
     { grammar_current_rule_end ((yylsp[0])); }
-#line 2582 "src/parse-gram.c" /* yacc.c:1646  */
+#line 2586 "src/parse-gram.c" /* yacc.c:1646  */
     break;
 
   case 85:
-#line 603 "src/parse-gram.y" /* yacc.c:1646  */
+#line 605 "src/parse-gram.y" /* yacc.c:1646  */
     { grammar_current_rule_end ((yylsp[0])); }
-#line 2588 "src/parse-gram.c" /* yacc.c:1646  */
+#line 2592 "src/parse-gram.c" /* yacc.c:1646  */
     break;
 
   case 87:
-#line 610 "src/parse-gram.y" /* yacc.c:1646  */
+#line 612 "src/parse-gram.y" /* yacc.c:1646  */
     { grammar_current_rule_begin (current_lhs_symbol, current_lhs_location,
                                   current_lhs_named_ref); }
-#line 2595 "src/parse-gram.c" /* yacc.c:1646  */
+#line 2599 "src/parse-gram.c" /* yacc.c:1646  */
     break;
 
   case 88:
-#line 613 "src/parse-gram.y" /* yacc.c:1646  */
+#line 615 "src/parse-gram.y" /* yacc.c:1646  */
     { grammar_current_rule_symbol_append ((yyvsp[-1].symbol), (yylsp[-1]), (yyvsp[0].named_ref)); }
-#line 2601 "src/parse-gram.c" /* yacc.c:1646  */
+#line 2605 "src/parse-gram.c" /* yacc.c:1646  */
     break;
 
   case 89:
-#line 615 "src/parse-gram.y" /* yacc.c:1646  */
+#line 617 "src/parse-gram.y" /* yacc.c:1646  */
     { grammar_current_rule_action_append ((yyvsp[-1].code), (yylsp[-1]), (yyvsp[0].named_ref), false); }
-#line 2607 "src/parse-gram.c" /* yacc.c:1646  */
+#line 2611 "src/parse-gram.c" /* yacc.c:1646  */
     break;
 
   case 90:
-#line 617 "src/parse-gram.y" /* yacc.c:1646  */
+#line 619 "src/parse-gram.y" /* yacc.c:1646  */
     { grammar_current_rule_action_append ((yyvsp[0].code), (yylsp[0]), NULL, true); }
-#line 2613 "src/parse-gram.c" /* yacc.c:1646  */
+#line 2617 "src/parse-gram.c" /* yacc.c:1646  */
     break;
 
   case 91:
-#line 619 "src/parse-gram.y" /* yacc.c:1646  */
+#line 621 "src/parse-gram.y" /* yacc.c:1646  */
     { grammar_current_rule_empty_set ((yylsp[0])); }
-#line 2619 "src/parse-gram.c" /* yacc.c:1646  */
+#line 2623 "src/parse-gram.c" /* yacc.c:1646  */
     break;
 
   case 92:
-#line 621 "src/parse-gram.y" /* yacc.c:1646  */
+#line 623 "src/parse-gram.y" /* yacc.c:1646  */
     { grammar_current_rule_prec_set ((yyvsp[0].symbol), (yylsp[0])); }
-#line 2625 "src/parse-gram.c" /* yacc.c:1646  */
+#line 2629 "src/parse-gram.c" /* yacc.c:1646  */
     break;
 
   case 93:
-#line 623 "src/parse-gram.y" /* yacc.c:1646  */
+#line 625 "src/parse-gram.y" /* yacc.c:1646  */
     { grammar_current_rule_dprec_set ((yyvsp[0].integer), (yylsp[0])); }
-#line 2631 "src/parse-gram.c" /* yacc.c:1646  */
+#line 2635 "src/parse-gram.c" /* yacc.c:1646  */
     break;
 
   case 94:
-#line 625 "src/parse-gram.y" /* yacc.c:1646  */
+#line 627 "src/parse-gram.y" /* yacc.c:1646  */
     { grammar_current_rule_merge_set ((yyvsp[0].uniqstr), (yylsp[0])); }
-#line 2637 "src/parse-gram.c" /* yacc.c:1646  */
+#line 2641 "src/parse-gram.c" /* yacc.c:1646  */
     break;
 
   case 95:
-#line 629 "src/parse-gram.y" /* yacc.c:1646  */
+#line 631 "src/parse-gram.y" /* yacc.c:1646  */
     { (yyval.named_ref) = 0; }
-#line 2643 "src/parse-gram.c" /* yacc.c:1646  */
+#line 2647 "src/parse-gram.c" /* yacc.c:1646  */
     break;
 
   case 96:
-#line 630 "src/parse-gram.y" /* yacc.c:1646  */
+#line 632 "src/parse-gram.y" /* yacc.c:1646  */
     { (yyval.named_ref) = named_ref_new ((yyvsp[0].uniqstr), (yylsp[0])); }
-#line 2649 "src/parse-gram.c" /* yacc.c:1646  */
+#line 2653 "src/parse-gram.c" /* yacc.c:1646  */
     break;
 
   case 98:
-#line 641 "src/parse-gram.y" /* yacc.c:1646  */
+#line 643 "src/parse-gram.y" /* yacc.c:1646  */
     { (yyval.uniqstr) = uniqstr_new ((yyvsp[0].code)); }
-#line 2655 "src/parse-gram.c" /* yacc.c:1646  */
+#line 2659 "src/parse-gram.c" /* yacc.c:1646  */
     break;
 
   case 99:
-#line 666 "src/parse-gram.y" /* yacc.c:1646  */
+#line 668 "src/parse-gram.y" /* yacc.c:1646  */
     { (yyval.value).kind = muscle_keyword; (yyval.value).chars = ""; }
-#line 2661 "src/parse-gram.c" /* yacc.c:1646  */
+#line 2665 "src/parse-gram.c" /* yacc.c:1646  */
     break;
 
   case 100:
-#line 667 "src/parse-gram.y" /* yacc.c:1646  */
+#line 669 "src/parse-gram.y" /* yacc.c:1646  */
     { (yyval.value).kind = muscle_keyword; (yyval.value).chars = (yyvsp[0].uniqstr); }
-#line 2667 "src/parse-gram.c" /* yacc.c:1646  */
+#line 2671 "src/parse-gram.c" /* yacc.c:1646  */
     break;
 
   case 101:
-#line 668 "src/parse-gram.y" /* yacc.c:1646  */
+#line 670 "src/parse-gram.y" /* yacc.c:1646  */
     { (yyval.value).kind = muscle_string;  (yyval.value).chars = (yyvsp[0].code); }
-#line 2673 "src/parse-gram.c" /* yacc.c:1646  */
+#line 2677 "src/parse-gram.c" /* yacc.c:1646  */
     break;
 
   case 102:
-#line 669 "src/parse-gram.y" /* yacc.c:1646  */
+#line 671 "src/parse-gram.y" /* yacc.c:1646  */
     { (yyval.value).kind = muscle_code;    (yyval.value).chars = strip_braces ((yyvsp[0].code)); }
-#line 2679 "src/parse-gram.c" /* yacc.c:1646  */
+#line 2683 "src/parse-gram.c" /* yacc.c:1646  */
     break;
 
   case 103:
-#line 682 "src/parse-gram.y" /* yacc.c:1646  */
+#line 684 "src/parse-gram.y" /* yacc.c:1646  */
     { (yyval.symbol) = symbol_from_uniqstr ((yyvsp[0].uniqstr), (yylsp[0])); }
-#line 2685 "src/parse-gram.c" /* yacc.c:1646  */
+#line 2689 "src/parse-gram.c" /* yacc.c:1646  */
     break;
 
   case 104:
-#line 684 "src/parse-gram.y" /* yacc.c:1646  */
+#line 686 "src/parse-gram.y" /* yacc.c:1646  */
     {
       (yyval.symbol) = symbol_get (char_name ((yyvsp[0].character)), (yylsp[0]));
       symbol_class_set ((yyval.symbol), token_sym, (yylsp[0]), false);
       symbol_user_token_number_set ((yyval.symbol), (yyvsp[0].character), (yylsp[0]));
     }
-#line 2695 "src/parse-gram.c" /* yacc.c:1646  */
+#line 2699 "src/parse-gram.c" /* yacc.c:1646  */
     break;
 
   case 105:
-#line 692 "src/parse-gram.y" /* yacc.c:1646  */
+#line 694 "src/parse-gram.y" /* yacc.c:1646  */
     { (yyval.symbol) = symbol_from_uniqstr ((yyvsp[0].uniqstr), (yylsp[0])); }
-#line 2701 "src/parse-gram.c" /* yacc.c:1646  */
+#line 2705 "src/parse-gram.c" /* yacc.c:1646  */
     break;
 
   case 108:
-#line 704 "src/parse-gram.y" /* yacc.c:1646  */
+#line 706 "src/parse-gram.y" /* yacc.c:1646  */
     {
       (yyval.symbol) = symbol_get (quotearg_style (c_quoting_style, (yyvsp[0].code)), (yylsp[0]));
       symbol_class_set ((yyval.symbol), token_sym, (yylsp[0]), false);
     }
-#line 2710 "src/parse-gram.c" /* yacc.c:1646  */
+#line 2714 "src/parse-gram.c" /* yacc.c:1646  */
     break;
 
   case 110:
-#line 713 "src/parse-gram.y" /* yacc.c:1646  */
+#line 715 "src/parse-gram.y" /* yacc.c:1646  */
     {
       muscle_code_grow ("epilogue", translate_code ((yyvsp[0].code), (yylsp[0]), true), (yylsp[0]));
       code_scanner_last_string_free ();
     }
-#line 2719 "src/parse-gram.c" /* yacc.c:1646  */
+#line 2723 "src/parse-gram.c" /* yacc.c:1646  */
     break;
 
 
-#line 2723 "src/parse-gram.c" /* yacc.c:1646  */
+#line 2727 "src/parse-gram.c" /* yacc.c:1646  */
         default: break;
       }
     if (yychar_backup != yychar)
@@ -2966,7 +2970,7 @@ yyreturn:
 #endif
   return yyresult;
 }
-#line 719 "src/parse-gram.y" /* yacc.c:1906  */
+#line 721 "src/parse-gram.y" /* yacc.c:1906  */
 
 
 /* Return the location of the left-hand side of a rule whose
diff --git a/src/parse-gram.h b/src/parse-gram.h
index b2c6e59b..c40151da 100644
--- a/src/parse-gram.h
+++ b/src/parse-gram.h
@@ -61,7 +61,7 @@ extern int gram_debug;
     param_parse  = 1 << 1,
     param_both   = param_lex | param_parse
   } param_type;
-#line 645 "src/parse-gram.y" /* yacc.c:1909  */
+#line 647 "src/parse-gram.y" /* yacc.c:1909  */
 #include "muscle-tab.h"
 
 #line 68 "src/parse-gram.h" /* yacc.c:1909  */
@@ -132,7 +132,7 @@ extern int gram_debug;
 
 /* Value type.  */
 #if ! defined GRAM_STYPE && ! defined GRAM_STYPE_IS_DECLARED
-typedef union GRAM_STYPE GRAM_STYPE;
+
 union GRAM_STYPE
 {
 #line 182 "src/parse-gram.y" /* yacc.c:1909  */
@@ -155,7 +155,7 @@ named_ref *named_ref;
 param_type param;
 #line 409 "src/parse-gram.y" /* yacc.c:1909  */
 code_props_type code_type;
-#line 647 "src/parse-gram.y" /* yacc.c:1909  */
+#line 649 "src/parse-gram.y" /* yacc.c:1909  */
 
   struct
   {
@@ -165,6 +165,8 @@ code_props_type code_type;
 
 #line 167 "src/parse-gram.h" /* yacc.c:1909  */
 };
+
+typedef union GRAM_STYPE GRAM_STYPE;
 # define GRAM_STYPE_IS_TRIVIAL 1
 # define GRAM_STYPE_IS_DECLARED 1
 #endif
diff --git a/src/parse-gram.y b/src/parse-gram.y
index 39431ef7..9184d5f8 100644
--- a/src/parse-gram.y
+++ b/src/parse-gram.y
@@ -421,7 +421,9 @@ code_props_type:
 
 union_name:
   %empty {}
-| ID     { muscle_code_grow ("union_name", $1, @1); }
+| ID     { muscle_percent_define_insert ("api.value.union.name",
+                                         @1, muscle_keyword, $1,
+                                         MUSCLE_PERCENT_DEFINE_GRAMMAR_FILE); }
 ;
 
 grammar_declaration:
diff --git a/tests/input.at b/tests/input.at
index 9e9296aa..895ec202 100644
--- a/tests/input.at
+++ b/tests/input.at
@@ -1904,6 +1904,51 @@ m4_popdef([AT_TEST])
 AT_CLEANUP
 
 
+## ----------------------- ##
+## Redefined %union name.  ##
+## ----------------------- ##
+
+AT_SETUP([[Redefined %union name]])
+
+# AT_TEST(DIRECTIVES, ERROR)
+# --------------------------
+m4_pushdef([AT_TEST],
+[AT_DATA([[input.y]],
+[$1
+%%
+exp: %empty;
+])
+
+AT_BISON_CHECK([[input.y]], [[1]], [[]],
+[$2])
+])
+
+AT_TEST([[%union foo {};
+%union {};
+%union foo {};
+%define api.value.union.name foo]],
+[[input.y:3.8-10: error: %define variable 'api.value.union.name' redefined
+input.y:1.8-10:     previous definition
+input.y:4.9-28: error: %define variable 'api.value.union.name' redefined
+input.y:3.8-10:     previous definition
+]])
+
+AT_TEST([[%define api.value.union.name {foo}]],
+[[input.y:1.9-28: error: %define variable 'api.value.union.name' requires keyword values
+input.y:1.9-28: error: %define variable 'api.value.union.name' is not used
+]])
+
+AT_TEST([[%define api.value.union.name "foo"]],
+[[input.y:1.9-28: error: %define variable 'api.value.union.name' requires keyword values
+input.y:1.9-28: error: %define variable 'api.value.union.name' is not used
+]])
+
+m4_popdef([AT_TEST])
+AT_CLEANUP
+
+
+
+
 ## -------------- ##
 ## Stray $ or @.  ##
 ## -------------- ##
diff --git a/tests/synclines.at b/tests/synclines.at
index de132f43..260e2f9e 100644
--- a/tests/synclines.at
+++ b/tests/synclines.at
@@ -182,6 +182,35 @@ exp: '0';
 ])
 
 
+## ---------------------- ##
+## %union name syncline.  ##
+## ---------------------- ##
+
+# Check that invalid union names are properly reported in the
+# source file.
+AT_SETUP([%union name syncline])
+AT_BISON_OPTION_PUSHDEFS
+AT_DATA([[input.y]],
+[[%union break
+{
+  char dummy;
+}
+%{
+]AT_YYERROR_DECLARE_EXTERN[
+]AT_YYLEX_DECLARE_EXTERN[
+%}
+%%
+exp: '0';
+%%
+]])
+
+AT_BISON_CHECK([-o input.c input.y])
+AT_SYNCLINES_COMPILE([input.c])
+AT_CHECK([[grep '^input.y:1' stdout]], 0, [ignore])
+AT_BISON_OPTION_POPDEFS
+AT_CLEANUP
+
+
 ## ----------------------- ##
 ## Postprologue syncline.  ##
 ## ----------------------- ##
diff --git a/tests/types.at b/tests/types.at
index d735d83f..0c108d9d 100644
--- a/tests/types.at
+++ b/tests/types.at
@@ -197,18 +197,23 @@ m4_foreach([b4_skel], [[yacc.c], [glr.c], [lalr1.cc], [glr.cc]],
              AT_VAL.fval = .2f],
           [10 0.2])
 
-  # A %union.
-  AT_TEST([%skeleton "]b4_skel["
-           %union { float fval; int ival; };],
-          [%token <ival> '1';
-           %token <fval> '2';],
-          ['1' '2' { printf ("%d %2.1f\n", $1, $2); }],
-          ["12"],
-          [if (res == '1')
-             AT_VAL.ival = 10;
-           else
-             AT_VAL.fval = 0.2f],
-          [10 0.2])
+  # A %union and a named %union.  In C++ named %union is an error.
+  m4_foreach([b4_union],
+             [m4_bmatch(b4_skel, [\.cc$],
+                       [[%union]],
+                        [[%union], [%union foo],
+                         [%define api.value.union.name foo; %union]])],
+   [AT_TEST([%skeleton "]b4_skel["
+             ]b4_union[ { float fval; int ival; };],
+            [%token <ival> '1';
+             %token <fval> '2';],
+            ['1' '2' { printf ("%d %2.1f\n", $1, $2); }],
+            ["12"],
+            [if (res == '1')
+               AT_VAL.ival = 10;
+             else
+               AT_VAL.fval = 0.2f],
+            [10 0.2])])
 
   # A Bison-defined union.
   # The tokens names are not available directly in C++, we use their
@@ -249,3 +254,22 @@ m4_foreach([b4_skel], [[yacc.c], [glr.c], [lalr1.cc], [glr.cc]],
 
 m4_popdef([AT_TEST])
 m4_popdef([_AT_TEST])
+
+
+## ------------------- ##
+## C++: Named %union.  ##
+## ------------------- ##
+
+m4_foreach([b4_skel], [[lalr1.cc], [glr.cc]],
+[AT_SETUP([b4_skel: Named %union])
+AT_DATA([input.y],
+[%skeleton "]b4_skel["
+%union foo { float fval; int ival; };
+%%
+exp: %empty;
+])
+AT_BISON_CHECK([input.y], 1, [],
+[[input.y:2.8-10: error: named %union is invalid in C++
+]])
+AT_CLEANUP
+])