diff --git a/src/sessions.ts b/src/sessions.ts
index 20699d24ac..544bef897c 100644
--- a/src/sessions.ts
+++ b/src/sessions.ts
@@ -174,7 +174,7 @@ export class ClientSession extends TypedEventEmitter<ClientSessionEvents> {
     this.sessionPool = sessionPool;
     this.hasEnded = false;
     this.clientOptions = clientOptions;
-    this.timeoutMS = options.defaultTimeoutMS ?? client.options?.timeoutMS;
+    this.timeoutMS = options.defaultTimeoutMS ?? client.s.options?.timeoutMS;
 
     this.explicit = !!options.explicit;
     this[kServerSession] = this.explicit ? this.sessionPool.acquire() : null;
diff --git a/test/unit/sessions.test.ts b/test/unit/sessions.test.ts
index f889ed9c6a..390b89233a 100644
--- a/test/unit/sessions.test.ts
+++ b/test/unit/sessions.test.ts
@@ -333,7 +333,7 @@ describe('Sessions - unit', function () {
 
       before(() => {
         serverSessionSymbol = getSymbolFrom(
-          new ClientSession({}, serverSessionPool, {}),
+          new ClientSession(client, serverSessionPool, {}),
           'serverSession'
         );
       });