diff --git a/tag.c b/tag.c
index 38bf9134f..990134fe7 100644
--- a/tag.c
+++ b/tag.c
@@ -9,7 +9,10 @@ const char *tag_type = "tag";
 struct object *deref_tag(struct object *o, const char *warn, int warnlen)
 {
 	while (o && o->type == OBJ_TAG)
-		o = parse_object(((struct tag *)o)->tagged->sha1);
+		if (((struct tag *)o)->tagged)
+			o = parse_object(((struct tag *)o)->tagged->sha1);
+		else
+			o = NULL;
 	if (!o && warn) {
 		if (!warnlen)
 			warnlen = strlen(warn);