free(tree->buffer);
        tree->buffer = NULL;
        tree->size = 0;
+       tree->object.parsed = 0;
        return 0;
 }
 
        if (!get_sha1_hex(target, sha1))
                return 0;
        if (!check_ref_format(target)) {
-               if (!walker->fetch_ref(walker, target, sha1)) {
+               struct ref *ref = alloc_ref_from_str(target);
+               if (!walker->fetch_ref(walker, ref)) {
+                       hashcpy(sha1, ref->old_sha1);
+                       free(ref);
                        return 0;
                }
+               free(ref);
        }
        return -1;
 }