diff --git a/ChangeLog b/ChangeLog
index 56fe9703..2315e33a 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,7 @@
+2001-11-22  Marc Autret  <autret_m@epita.fr>
+
+	* src/bison.simple [YYERROR_VERBOSE]: Force its value to be 1 or 0.
+
 2001-11-22  Marc Autret  <autret_m@epita.fr>
 
 	* src/muscle_tab.c (muscle_init): Remove initialization of
diff --git a/src/bison.simple b/src/bison.simple
index 67ac9a35..9b627b1c 100644
--- a/src/bison.simple
+++ b/src/bison.simple
@@ -151,6 +151,9 @@ typedef struct yyltype
 
 #ifndef YYERROR_VERBOSE
 # define YYERROR_VERBOSE %%verbose
+#else
+# undef YYERROR_VERBOSE
+# define YYERROR_VERBOSE 1
 #endif
 
 /* Tokens.  */