diff --git a/lib/asn1/asn1parse.y b/lib/asn1/asn1parse.y
index 9d8b76f58..91b163a28 100644
--- a/lib/asn1/asn1parse.y
+++ b/lib/asn1/asn1parse.y
@@ -65,6 +65,7 @@ static void validate_object_set(IOSObjectSet *);
 static struct constraint_spec *new_constraint_spec(enum ctype);
 static Type *new_tag(int tagclass, int tagvalue, int tagenv, Type *oldtype);
 void yyerror (const char *);
+#define yyerror yyerror
 static struct objid *new_objid(const char *label, int value);
 static void add_oid_to_tail(struct objid *, struct objid *);
 static void fix_labels(Symbol *s);
diff --git a/lib/com_err/parse.y b/lib/com_err/parse.y
index 0c2e5084b..bcb9b0520 100644
--- a/lib/com_err/parse.y
+++ b/lib/com_err/parse.y
@@ -35,7 +35,8 @@
 #include "compile_et.h"
 #include "lex.h"
 
-void yyerror (char *s);
+void yyerror (const char *s);
+#define yyerror yyerror
 static long name2number(const char *str);
 
 extern char *yytext;
@@ -168,7 +169,7 @@ name2number(const char *str)
 }
 
 void
-yyerror (char *s)
+yyerror (const char *s)
 {
      _lex_error_message ("%s\n", s);
 }
diff --git a/lib/sl/slc-lex.l b/lib/sl/slc-lex.l
index 50965bccd..3a3730233 100644
--- a/lib/sl/slc-lex.l
+++ b/lib/sl/slc-lex.l
@@ -78,7 +78,7 @@ error_message (const char *format, ...)
 }
 
 void
-yyerror (char *s)
+yyerror (const char *s)
 {
     error_message("%s\n", s);
 }
diff --git a/lib/sl/slc.h b/lib/sl/slc.h
index 6e45ed2f1..e4dc2cba6 100644
--- a/lib/sl/slc.h
+++ b/lib/sl/slc.h
@@ -51,5 +51,6 @@ extern char *filename;
 extern int error_flag;
 void error_message (const char *format, ...);
 int yylex(void);
-void yyerror (char *s);
+void yyerror (const char *s);
+#define yyerror yyerror
 extern unsigned lineno;