diff --git a/src/language.yacc b/src/language.yacc
index 69c3138a5a917fbe81e6639aa18f12c6f95e9a14..3f57b962b27f7c2899e25fd5982f7abb9eeb5959 100644
--- a/src/language.yacc
+++ b/src/language.yacc
@@ -188,7 +188,7 @@
 /* This is the grammar definition of Pike. */
 
 #include "global.h"
-RCSID("$Id: language.yacc,v 1.172 2000/03/30 18:59:32 grubba Exp $");
+RCSID("$Id: language.yacc,v 1.173 2000/03/30 19:01:38 grubba Exp $");
 #ifdef HAVE_MEMORY_H
 #include <memory.h>
 #endif
@@ -1242,6 +1242,7 @@ opt_function_type: '('
       if (!$3) {
 	/* FIXME: Should this be a syntax error or not? */
 	push_type(T_MIXED);
+	yywarning("Implicit mixed type.");
       }
       push_type(T_MANY);
       type_stack_reverse();