From a28c30fbf9205f7e8ea19902b87141f492e5384a Mon Sep 17 00:00:00 2001
From: Jiachi Liu <inbox@huozhi.im>
Date: Thu, 10 Mar 2022 22:14:56 +0100
Subject: [PATCH] check return value

---
 packages/next/server/web/sandbox/readable-stream.ts | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/packages/next/server/web/sandbox/readable-stream.ts b/packages/next/server/web/sandbox/readable-stream.ts
index 7a845444b81d..7c0a1a43bd48 100644
--- a/packages/next/server/web/sandbox/readable-stream.ts
+++ b/packages/next/server/web/sandbox/readable-stream.ts
@@ -68,7 +68,7 @@ class ReadableStream<T> {
     }
 
     const started = opts.start && opts.start(controller)
-    if (typeof started.then === 'function') {
+    if (started && typeof started.then === 'function') {
       started.then(() => registerPull())
     } else {
       registerPull()