diff --git a/THANKS b/THANKS
index 52298d08..d964c10a 100644
--- a/THANKS
+++ b/THANKS
@@ -40,6 +40,7 @@ Daniel Hagerty            hag@gnu.org
 David J. MacKenzie        djm@gnu.org
 David Kastrup             dak@gnu.org
 Dennis Clarke             dclarke@blastwave.org
+Derek Clegg               derek@me.com
 Derek M. Jones            derek@knosof.co.uk
 Di-an Jan                 dianj@freeshell.org
 Dick Streefland           dick.streefland@altium.nl
diff --git a/configure.ac b/configure.ac
index 5412f6b9..99f6ad43 100644
--- a/configure.ac
+++ b/configure.ac
@@ -94,7 +94,7 @@ if test "$enable_gcc_warnings" = yes; then
   # -Wno-keyword-macro: We use the "#define private public" dirty
   # trick in the test suite to check some private implementation
   # details for lalr1.cc.
-  warn_tests='-Wundef -pedantic -Wsign-compare -fno-color-diagnostics
+  warn_tests='-Wundef -pedantic -Wdeprecated -Wsign-compare -fno-color-diagnostics
     -Wno-keyword-macro'
 
   AC_LANG_PUSH([C])
diff --git a/data/lalr1.cc b/data/lalr1.cc
index a4feab0a..5ac9d2de 100644
--- a/data/lalr1.cc
+++ b/data/lalr1.cc
@@ -314,6 +314,8 @@ b4_location_define])])[
       typedef basic_symbol<by_state> super_type;
       /// Construct an empty symbol.
       stack_symbol_type ();
+      /// Copy construct.
+      stack_symbol_type (const stack_symbol_type& that);
       /// Steal the contents from \a sym to build this.
       stack_symbol_type (state_type s, symbol_type& sym);
       /// Assignment, needed by push_back.
@@ -573,6 +575,13 @@ m4_if(b4_prefix, [yy], [],
   ]b4_parser_class_name[::stack_symbol_type::stack_symbol_type ()
   {}
 
+  ]b4_parser_class_name[::stack_symbol_type::stack_symbol_type (const stack_symbol_type& that)
+    : super_type (that.state]b4_locations_if([, that.location])[)
+  {
+    ]b4_variant_if([b4_symbol_variant([that.type_get ()],
+                                      [value], [copy], [that.value])],
+                   [[value = that.value;]])[
+  }
 
   ]b4_parser_class_name[::stack_symbol_type::stack_symbol_type (state_type s, symbol_type& that)
     : super_type (s]b4_locations_if([, that.location])[)