diff --git a/‎packages/socket.io-cluster-engine/lib/engine.ts‎
Lines changed: 4 additions & 0 deletions b/‎packages/socket.io-cluster-engine/lib/engine.ts‎
Lines changed: 4 additions & 0 deletions
diff --git a/‎packages/socket.io-cluster-engine/test/in-memory.test.ts‎
Lines changed: 19 additions & 8 deletions b/‎packages/socket.io-cluster-engine/test/in-memory.test.ts‎
Lines changed: 19 additions & 8 deletions
@@ -213,6 +213,10 @@ export abstract class ClusterEngine extends Server {
           },
         });
 
+        if (!success) {
+          break;
+        }
+
         switch (transportName) {
           case "polling": {
             if (message.data.type === "read") {
 
@@ -161,16 +161,27 @@ describe("in-memory", () => {
   it("should acquire read lock (different process)", async () => {
     const sid = await handshake(ports[0]);
 
-    const controller = new AbortController();
-    const fetchPromise = fetch(url(ports[0], sid), {
-      signal: controller.signal,
-    }).catch(() => {});
+    // acquire lock
+    const fetchPromise = fetch(url(ports[0], sid));
+
+    {
+      // check that the SID is locked for reading
+      const res = await fetch(url(ports[1], sid));
+      assert.equal(res.status, 400);
+      // @ts-expect-error protected property
+      assert.equal(engine2.clients[sid], undefined);
+    }
 
-    const res = await fetch(url(ports[1], sid));
-    assert.equal(res.status, 400);
+    {
+      // check that the lock works
+      // @ts-expect-error protected property
+      engine1.clients[sid]!.send("hello");
 
-    controller.abort();
-    await fetchPromise;
+      const res = await fetchPromise;
+      const body = await res.text();
+
+      assert.equal(body, "4hello");
+    }
   });
 
   it("should acquire read lock (same process)", async () => {