diff --git a/src/hooks/useChatbot.ts b/src/hooks/useChatbot.ts
index 600a34e..f2c0a2e 100644
--- a/src/hooks/useChatbot.ts
+++ b/src/hooks/useChatbot.ts
@@ -341,7 +341,7 @@ export function useChatbot(): ChatbotHookReturn {
     if (!workflowIdToStop && messages.length > 0) {
       // Try to extract workflowId from the latest message (supports workflowId and conversationId)
       const latestMessage = messages[messages.length - 1];
-      workflowIdToStop = getConversationId(latestMessage) || undefined;
+      workflowIdToStop = getConversationId(latestMessage) ?? null;
       if (workflowIdToStop) {
         console.log('Extracted workflowId from latest message:', workflowIdToStop);
       }