diff --git a/packages/core-internal/src/shared/protocol.ts b/packages/core-internal/src/shared/protocol.ts
index 0a19770082..ead715f5bf 100644
--- a/packages/core-internal/src/shared/protocol.ts
+++ b/packages/core-internal/src/shared/protocol.ts
@@ -724,7 +724,7 @@ export abstract class Protocol<ContextT extends BaseContext> {
     }
 
     private async _oncancel(notification: CancelledNotification): Promise<void> {
-        if (!notification.params.requestId) {
+        if (notification.params.requestId === undefined) {
             return;
         }
         // Handle request cancellation
diff --git a/packages/core-internal/test/shared/protocol.test.ts b/packages/core-internal/test/shared/protocol.test.ts
index 2ecdc40adc..5b979add5d 100644
--- a/packages/core-internal/test/shared/protocol.test.ts
+++ b/packages/core-internal/test/shared/protocol.test.ts
@@ -775,7 +775,7 @@ describe('protocol tests', () => {
     });
 
     describe('notifications/cancelled behavior', () => {
-        test('should abort request handler when notifications/cancelled is received', async () => {
+        test('should abort request handler when notifications/cancelled contains requestId 0', async () => {
             await protocol.connect(transport);
 
             // Set up a request handler that checks if it was aborted
@@ -788,7 +788,7 @@ describe('protocol tests', () => {
             });
 
             // Simulate an incoming request
-            const requestId = 123;
+            const requestId = 0;
             if (transport.onmessage) {
                 transport.onmessage({
                     jsonrpc: '2.0',