diff --git a/src/symtab.c b/src/symtab.c
index 12e19ec9..ab3f12e7 100644
--- a/src/symtab.c
+++ b/src/symtab.c
@@ -147,7 +147,7 @@ semantic_type_new (uniqstr tag, const location *loc)
     fprintf (f, " %s { %s }", #Attr, s->props[Attr].code)
 
 void
-symbol_print (symbol *s, FILE *f)
+symbol_print (symbol const *s, FILE *f)
 {
   if (s)
     {
diff --git a/src/symtab.h b/src/symtab.h
index 4663a695..e2bf2d38 100644
--- a/src/symtab.h
+++ b/src/symtab.h
@@ -149,7 +149,7 @@ symbol *dummy_symbol_get (location loc);
 `--------------------*/
 
 /** Print a symbol (for debugging). */
-void symbol_print (symbol *s, FILE *f);
+void symbol_print (symbol const *s, FILE *f);
 
 /** Is this a dummy nonterminal?  */
 bool symbol_is_dummy (const symbol *sym);