diff --git a/web/app/components/base/chat/utils.ts b/web/app/components/base/chat/utils.ts
index b47fec1d0a..5881f565a4 100644
--- a/web/app/components/base/chat/utils.ts
+++ b/web/app/components/base/chat/utils.ts
@@ -158,7 +158,7 @@ function buildChatItemTree(allMessages: IChatItem[]): ChatItemInTree[] {
         rootNodes.push(questionNode)
       }
       else {
-        map[parentMessageId]?.children!.push(questionNode)
+        map[parentMessageId].children!.push(questionNode)
       }
     }
   }