diff --git a/lib/asn1/parse.y b/lib/asn1/parse.y
index 2f55a4804..3d292ecc2 100644
--- a/lib/asn1/parse.y
+++ b/lib/asn1/parse.y
@@ -53,7 +53,7 @@ RCSID("$Id$");
 
 static Type *new_type (Typetype t);
 void yyerror (char *);
-int yylex();
+int yylex(void);
 
 static void append (Member *l, Member *r);