diff --git a/merge.c b/merge.c
index a18a452..e5d796c 100644
--- a/merge.c
+++ b/merge.c
@@ -91,9 +91,7 @@ int checkout_fast_forward(const struct object_id *head,
 	}
 	if (unpack_trees(nr_trees, t, &opts))
 		return -1;
-	if (write_locked_index(&the_index, &lock_file, COMMIT_LOCK)) {
-		rollback_lock_file(&lock_file);
+	if (write_locked_index(&the_index, &lock_file, COMMIT_LOCK))
 		return error(_("unable to write new index file"));
-	}
 	return 0;
 }