diff --git a/refs.c b/refs.c
index e3c4ab5fd5..b9cf284f31 100644
--- a/refs.c
+++ b/refs.c
@@ -3690,6 +3690,8 @@ int ref_transaction_create(struct ref_transaction *transaction,
 			   unsigned int flags, const char *msg,
 			   struct strbuf *err)
 {
+	if (!new_sha1 || is_null_sha1(new_sha1))
+		die("BUG: create called without valid new_sha1");
 	return ref_transaction_update(transaction, refname, new_sha1,
 				      null_sha1, flags, msg, err);
 }