diff --git a/sha1_name.c b/sha1_name.c
index 8bc20c54b1..13c3d75e81 100644
--- a/sha1_name.c
+++ b/sha1_name.c
@@ -241,7 +241,7 @@ static int disambiguate_committish_only(const unsigned char *sha1, void *cb_data
 		return 0;
 
 	/* We need to do this the hard way... */
-	obj = deref_tag(lookup_object(sha1), NULL, 0);
+	obj = deref_tag(parse_object(sha1), NULL, 0);
 	if (obj && obj->type == OBJ_COMMIT)
 		return 1;
 	return 0;