diff --git a/builtin/diff-tree.c b/builtin/diff-tree.c
index be6417d166..dddd0f9188 100644
--- a/builtin/diff-tree.c
+++ b/builtin/diff-tree.c
@@ -72,9 +72,7 @@ static int diff_tree_stdin(char *line)
 	line[len-1] = 0;
 	if (get_sha1_hex(line, sha1))
 		return -1;
-	obj = lookup_unknown_object(sha1);
-	if (!obj || !obj->parsed)
-		obj = parse_object(sha1);
+	obj = parse_object(sha1);
 	if (!obj)
 		return -1;
 	if (obj->type == OBJ_COMMIT)