diff --git a/builtin/describe.c b/builtin/describe.c
index 66fc291..9f63067 100644
--- a/builtin/describe.c
+++ b/builtin/describe.c
@@ -462,8 +462,21 @@
 		die(_("No names found, cannot describe anything."));
 
 	if (argc == 0) {
-		if (dirty && !cmd_diff_index(ARRAY_SIZE(diff_index_args) - 1, diff_index_args, prefix))
-			dirty = NULL;
+		if (dirty) {
+			static struct lock_file index_lock;
+			int fd;
+
+			read_cache_preload(NULL);
+			refresh_index(&the_index, REFRESH_QUIET|REFRESH_UNMERGED,
+				      NULL, NULL, NULL);
+			fd = hold_locked_index(&index_lock, 0);
+			if (0 <= fd)
+				update_index_if_able(&the_index, &index_lock);
+
+			if (!cmd_diff_index(ARRAY_SIZE(diff_index_args) - 1,
+					    diff_index_args, prefix))
+				dirty = NULL;
+		}
 		describe("HEAD", 1);
 	} else if (dirty) {
 		die(_("--dirty is incompatible with committishes"));