diff --git a/docs/enums/common.CloseCode.md b/docs/enums/common.CloseCode.md
index 56f3e3e6..be09deb9 100644
--- a/docs/enums/common.CloseCode.md
+++ b/docs/enums/common.CloseCode.md
@@ -11,6 +11,7 @@
 ### Enumeration members
 
 - [BadRequest](common.CloseCode.md#badrequest)
+- [ConnectionAcknowledgementTimeout](common.CloseCode.md#connectionacknowledgementtimeout)
 - [ConnectionInitialisationTimeout](common.CloseCode.md#connectioninitialisationtimeout)
 - [Forbidden](common.CloseCode.md#forbidden)
 - [InternalServerError](common.CloseCode.md#internalservererror)
@@ -27,6 +28,12 @@
 
 ___
 
+### ConnectionAcknowledgementTimeout
+
+• **ConnectionAcknowledgementTimeout** = `4504`
+
+___
+
 ### ConnectionInitialisationTimeout
 
 • **ConnectionInitialisationTimeout** = `4408`
diff --git a/docs/interfaces/client.ClientOptions.md b/docs/interfaces/client.ClientOptions.md
index 41655403..66ff6063 100644
--- a/docs/interfaces/client.ClientOptions.md
+++ b/docs/interfaces/client.ClientOptions.md
@@ -10,6 +10,7 @@ Configuration used for the GraphQL over WebSocket client.
 
 ### Properties
 
+- [connectionAckWaitTimeout](client.ClientOptions.md#connectionackwaittimeout)
 - [connectionParams](client.ClientOptions.md#connectionparams)
 - [disablePong](client.ClientOptions.md#disablepong)
 - [jsonMessageReplacer](client.ClientOptions.md#jsonmessagereplacer)
@@ -31,6 +32,24 @@ Configuration used for the GraphQL over WebSocket client.
 
 ## Properties
 
+### connectionAckWaitTimeout
+
+• `Optional` **connectionAckWaitTimeout**: `number`
+
+The amount of time for which the client will wait
+for `ConnectionAck` message.
+
+Set the value to `Infinity`, `''`, `0`, `null` or `undefined` to skip waiting.
+
+If the wait timeout has passed and the server
+has not responded with `ConnectionAck` message,
+the client will terminate the socket by
+dispatching a close event `4418: Connection acknowledgement timeout`
+
+**`default`** 0
+
+___
+
 ### connectionParams
 
 • `Optional` **connectionParams**: `Record`<`string`, `unknown`\> \| () => `undefined` \| `Record`<`string`, `unknown`\> \| `Promise`<`undefined` \| `Record`<`string`, `unknown`\>\>
diff --git a/src/__tests__/client.ts b/src/__tests__/client.ts
index 8b3d3cd4..7c965e08 100644
--- a/src/__tests__/client.ts
+++ b/src/__tests__/client.ts
@@ -405,6 +405,31 @@ it('should use a custom JSON message replacer function', async (done) => {
   });
 });
 
+it('should close socket if connection not acknowledged', async (done) => {
+  const { url, ...server } = await startTServer({
+    onConnect: () =>
+      new Promise(() => {
+        // never acknowledge
+      }),
+  });
+
+  const client = createClient({
+    url,
+    lazy: false,
+    retryAttempts: 0,
+    onNonLazyError: noop,
+    connectionAckWaitTimeout: 10,
+  });
+
+  client.on('closed', async (err) => {
+    expect((err as CloseEvent).code).toBe(
+      CloseCode.ConnectionAcknowledgementTimeout,
+    );
+    await server.dispose();
+    done();
+  });
+});
+
 describe('ping/pong', () => {
   it('should respond with a pong to a ping', async () => {
     expect.assertions(1);
diff --git a/src/client.ts b/src/client.ts
index 26755806..fc215a62 100644
--- a/src/client.ts
+++ b/src/client.ts
@@ -304,6 +304,20 @@ export interface ClientOptions {
    * @default 0
    */
   keepAlive?: number;
+  /**
+   * The amount of time for which the client will wait
+   * for `ConnectionAck` message.
+   *
+   * Set the value to `Infinity`, `''`, `0`, `null` or `undefined` to skip waiting.
+   *
+   * If the wait timeout has passed and the server
+   * has not responded with `ConnectionAck` message,
+   * the client will terminate the socket by
+   * dispatching a close event `4418: Connection acknowledgement timeout`
+   *
+   * @default 0
+   */
+  connectionAckWaitTimeout?: number;
   /**
    * Disable sending the `PongMessage` automatically.
    *
@@ -423,6 +437,7 @@ export function createClient(options: ClientOptions): Client {
     lazyCloseTimeout = 0,
     keepAlive = 0,
     disablePong,
+    connectionAckWaitTimeout = 0,
     retryAttempts = 5,
     retryWait = async function randomisedExponentialBackoff(retries) {
       let retryDelay = 1000; // start with 1s delay
@@ -562,7 +577,8 @@ export function createClient(options: ClientOptions): Client {
             GRAPHQL_TRANSPORT_WS_PROTOCOL,
           );
 
-          let queuedPing: ReturnType<typeof setTimeout>;
+          let connectionAckTimeout: ReturnType<typeof setTimeout>,
+            queuedPing: ReturnType<typeof setTimeout>;
           function enqueuePing() {
             if (isFinite(keepAlive) && keepAlive > 0) {
               clearTimeout(queuedPing); // in case where a pong was received before a ping (this is valid behaviour)
@@ -582,6 +598,7 @@ export function createClient(options: ClientOptions): Client {
 
           socket.onclose = (event) => {
             connecting = undefined;
+            clearTimeout(connectionAckTimeout);
             clearTimeout(queuedPing);
             emitter.emit('closed', event);
             denied(event);
@@ -608,6 +625,19 @@ export function createClient(options: ClientOptions): Client {
                   replacer,
                 ),
               );
+
+              if (
+                isFinite(connectionAckWaitTimeout) &&
+                connectionAckWaitTimeout > 0
+              ) {
+                connectionAckTimeout = setTimeout(() => {
+                  socket.close(
+                    CloseCode.ConnectionAcknowledgementTimeout,
+                    'Connection acknowledgement timeout',
+                  );
+                }, connectionAckWaitTimeout);
+              }
+
               enqueuePing(); // enqueue ping (noop if disabled)
             } catch (err) {
               socket.close(
@@ -651,6 +681,7 @@ export function createClient(options: ClientOptions): Client {
                 throw new Error(
                   `First message cannot be of type ${message.type}`,
                 );
+              clearTimeout(connectionAckTimeout);
               acknowledged = true;
               emitter.emit('connected', socket, message.payload); // connected = socket opened + acknowledged
               retrying = false; // future lazy connects are not retries
@@ -723,6 +754,7 @@ export function createClient(options: ClientOptions): Client {
           // CloseCode.Forbidden, might grant access out after retry
           CloseCode.SubprotocolNotAcceptable,
           // CloseCode.ConnectionInitialisationTimeout, might not time out after retry
+          // CloseCode.ConnectionAcknowledgementTimeout, might not time out after retry
           CloseCode.SubscriberAlreadyExists,
           CloseCode.TooManyInitialisationRequests,
         ].includes(errOrCloseEvent.code))
diff --git a/src/common.ts b/src/common.ts
index ae08b48d..b6bfa84e 100644
--- a/src/common.ts
+++ b/src/common.ts
@@ -33,6 +33,7 @@ export enum CloseCode {
   Forbidden = 4403,
   SubprotocolNotAcceptable = 4406,
   ConnectionInitialisationTimeout = 4408,
+  ConnectionAcknowledgementTimeout = 4504,
   /** Subscriber distinction is very important */
   SubscriberAlreadyExists = 4409,
   TooManyInitialisationRequests = 4429,