diff --git a/libmb/hash.h b/libmb/hash.h
index 86f18bf..43827b2 100644
--- a/libmb/hash.h
+++ b/libmb/hash.h
@@ -38,5 +38,5 @@ struct hash* hash_new(int size);
 unsigned int hashfunc(struct hash *h, char *s);
 struct nlist *hash_lookup(struct hash *h, char *s);
 struct nlist *hash_add(struct hash *h, char *key, char *val);
-void hash_empty();
+void hash_empty(struct hash *h);
 void hash_destroy(struct hash *h);