diff --git a/baselines/audioworklet.generated.d.ts b/baselines/audioworklet.generated.d.ts
index 1d5a8086b..e23e869a6 100644
--- a/baselines/audioworklet.generated.d.ts
+++ b/baselines/audioworklet.generated.d.ts
@@ -682,14 +682,14 @@ interface MessageEventTargetEventMap {
     "messageerror": MessageEvent;
 }
 
-interface MessageEventTarget {
+interface MessageEventTarget<T> {
     /** [MDN Reference](https://developer.mozilla.org/docs/Web/API/DedicatedWorkerGlobalScope/message_event) */
-    onmessage: ((this: MessageEventTarget, ev: MessageEvent) => any) | null;
+    onmessage: ((this: MessageEventTarget<T>, ev: MessageEvent) => any) | null;
     /** [MDN Reference](https://developer.mozilla.org/docs/Web/API/DedicatedWorkerGlobalScope/messageerror_event) */
-    onmessageerror: ((this: MessageEventTarget, ev: MessageEvent) => any) | null;
-    addEventListener<K extends keyof MessageEventTargetEventMap>(type: K, listener: (this: MessageEventTarget, ev: MessageEventTargetEventMap[K]) => any, options?: boolean | AddEventListenerOptions): void;
+    onmessageerror: ((this: MessageEventTarget<T>, ev: MessageEvent) => any) | null;
+    addEventListener<K extends keyof MessageEventTargetEventMap>(type: K, listener: (this: MessageEventTarget<T>, ev: MessageEventTargetEventMap[K]) => any, options?: boolean | AddEventListenerOptions): void;
     addEventListener(type: string, listener: EventListenerOrEventListenerObject, options?: boolean | AddEventListenerOptions): void;
-    removeEventListener<K extends keyof MessageEventTargetEventMap>(type: K, listener: (this: MessageEventTarget, ev: MessageEventTargetEventMap[K]) => any, options?: boolean | EventListenerOptions): void;
+    removeEventListener<K extends keyof MessageEventTargetEventMap>(type: K, listener: (this: MessageEventTarget<T>, ev: MessageEventTargetEventMap[K]) => any, options?: boolean | EventListenerOptions): void;
     removeEventListener(type: string, listener: EventListenerOrEventListenerObject, options?: boolean | EventListenerOptions): void;
 }
 
@@ -703,7 +703,7 @@ interface MessagePortEventMap extends MessageEventTargetEventMap {
  *
  * [MDN Reference](https://developer.mozilla.org/docs/Web/API/MessagePort)
  */
-interface MessagePort extends EventTarget, MessageEventTarget {
+interface MessagePort extends EventTarget, MessageEventTarget<MessagePort> {
     /**
      * Disconnects the port, so that it is no longer active.
      *
diff --git a/baselines/dom.generated.d.ts b/baselines/dom.generated.d.ts
index bcae88127..792501007 100644
--- a/baselines/dom.generated.d.ts
+++ b/baselines/dom.generated.d.ts
@@ -16389,14 +16389,14 @@ interface MessageEventTargetEventMap {
     "messageerror": MessageEvent;
 }
 
-interface MessageEventTarget {
+interface MessageEventTarget<T> {
     /** [MDN Reference](https://developer.mozilla.org/docs/Web/API/DedicatedWorkerGlobalScope/message_event) */
-    onmessage: ((this: MessageEventTarget, ev: MessageEvent) => any) | null;
+    onmessage: ((this: MessageEventTarget<T>, ev: MessageEvent) => any) | null;
     /** [MDN Reference](https://developer.mozilla.org/docs/Web/API/DedicatedWorkerGlobalScope/messageerror_event) */
-    onmessageerror: ((this: MessageEventTarget, ev: MessageEvent) => any) | null;
-    addEventListener<K extends keyof MessageEventTargetEventMap>(type: K, listener: (this: MessageEventTarget, ev: MessageEventTargetEventMap[K]) => any, options?: boolean | AddEventListenerOptions): void;
+    onmessageerror: ((this: MessageEventTarget<T>, ev: MessageEvent) => any) | null;
+    addEventListener<K extends keyof MessageEventTargetEventMap>(type: K, listener: (this: MessageEventTarget<T>, ev: MessageEventTargetEventMap[K]) => any, options?: boolean | AddEventListenerOptions): void;
     addEventListener(type: string, listener: EventListenerOrEventListenerObject, options?: boolean | AddEventListenerOptions): void;
-    removeEventListener<K extends keyof MessageEventTargetEventMap>(type: K, listener: (this: MessageEventTarget, ev: MessageEventTargetEventMap[K]) => any, options?: boolean | EventListenerOptions): void;
+    removeEventListener<K extends keyof MessageEventTargetEventMap>(type: K, listener: (this: MessageEventTarget<T>, ev: MessageEventTargetEventMap[K]) => any, options?: boolean | EventListenerOptions): void;
     removeEventListener(type: string, listener: EventListenerOrEventListenerObject, options?: boolean | EventListenerOptions): void;
 }
 
@@ -16410,7 +16410,7 @@ interface MessagePortEventMap extends MessageEventTargetEventMap {
  *
  * [MDN Reference](https://developer.mozilla.org/docs/Web/API/MessagePort)
  */
-interface MessagePort extends EventTarget, MessageEventTarget {
+interface MessagePort extends EventTarget, MessageEventTarget<MessagePort> {
     /**
      * Disconnects the port, so that it is no longer active.
      *
@@ -27259,8 +27259,6 @@ interface WindowSessionStorage {
 }
 
 interface WorkerEventMap extends AbstractWorkerEventMap, MessageEventTargetEventMap {
-    "message": MessageEvent;
-    "messageerror": MessageEvent;
 }
 
 /**
@@ -27268,7 +27266,7 @@ interface WorkerEventMap extends AbstractWorkerEventMap, MessageEventTargetEvent
  *
  * [MDN Reference](https://developer.mozilla.org/docs/Web/API/Worker)
  */
-interface Worker extends EventTarget, AbstractWorker, MessageEventTarget {
+interface Worker extends EventTarget, AbstractWorker, MessageEventTarget<Worker> {
     /**
      * Clones message and transmits it to worker's global environment. transfer can be passed as a list of objects that are to be transferred rather than cloned.
      *
diff --git a/baselines/serviceworker.generated.d.ts b/baselines/serviceworker.generated.d.ts
index f848ec0fd..30cda9881 100644
--- a/baselines/serviceworker.generated.d.ts
+++ b/baselines/serviceworker.generated.d.ts
@@ -3759,14 +3759,14 @@ interface MessageEventTargetEventMap {
     "messageerror": MessageEvent;
 }
 
-interface MessageEventTarget {
+interface MessageEventTarget<T> {
     /** [MDN Reference](https://developer.mozilla.org/docs/Web/API/DedicatedWorkerGlobalScope/message_event) */
-    onmessage: ((this: MessageEventTarget, ev: MessageEvent) => any) | null;
+    onmessage: ((this: MessageEventTarget<T>, ev: MessageEvent) => any) | null;
     /** [MDN Reference](https://developer.mozilla.org/docs/Web/API/DedicatedWorkerGlobalScope/messageerror_event) */
-    onmessageerror: ((this: MessageEventTarget, ev: MessageEvent) => any) | null;
-    addEventListener<K extends keyof MessageEventTargetEventMap>(type: K, listener: (this: MessageEventTarget, ev: MessageEventTargetEventMap[K]) => any, options?: boolean | AddEventListenerOptions): void;
+    onmessageerror: ((this: MessageEventTarget<T>, ev: MessageEvent) => any) | null;
+    addEventListener<K extends keyof MessageEventTargetEventMap>(type: K, listener: (this: MessageEventTarget<T>, ev: MessageEventTargetEventMap[K]) => any, options?: boolean | AddEventListenerOptions): void;
     addEventListener(type: string, listener: EventListenerOrEventListenerObject, options?: boolean | AddEventListenerOptions): void;
-    removeEventListener<K extends keyof MessageEventTargetEventMap>(type: K, listener: (this: MessageEventTarget, ev: MessageEventTargetEventMap[K]) => any, options?: boolean | EventListenerOptions): void;
+    removeEventListener<K extends keyof MessageEventTargetEventMap>(type: K, listener: (this: MessageEventTarget<T>, ev: MessageEventTargetEventMap[K]) => any, options?: boolean | EventListenerOptions): void;
     removeEventListener(type: string, listener: EventListenerOrEventListenerObject, options?: boolean | EventListenerOptions): void;
 }
 
@@ -3780,7 +3780,7 @@ interface MessagePortEventMap extends MessageEventTargetEventMap {
  *
  * [MDN Reference](https://developer.mozilla.org/docs/Web/API/MessagePort)
  */
-interface MessagePort extends EventTarget, MessageEventTarget {
+interface MessagePort extends EventTarget, MessageEventTarget<MessagePort> {
     /**
      * Disconnects the port, so that it is no longer active.
      *
diff --git a/baselines/sharedworker.generated.d.ts b/baselines/sharedworker.generated.d.ts
index f2bb37e7a..9068ec8e5 100644
--- a/baselines/sharedworker.generated.d.ts
+++ b/baselines/sharedworker.generated.d.ts
@@ -3648,14 +3648,14 @@ interface MessageEventTargetEventMap {
     "messageerror": MessageEvent;
 }
 
-interface MessageEventTarget {
+interface MessageEventTarget<T> {
     /** [MDN Reference](https://developer.mozilla.org/docs/Web/API/DedicatedWorkerGlobalScope/message_event) */
-    onmessage: ((this: MessageEventTarget, ev: MessageEvent) => any) | null;
+    onmessage: ((this: MessageEventTarget<T>, ev: MessageEvent) => any) | null;
     /** [MDN Reference](https://developer.mozilla.org/docs/Web/API/DedicatedWorkerGlobalScope/messageerror_event) */
-    onmessageerror: ((this: MessageEventTarget, ev: MessageEvent) => any) | null;
-    addEventListener<K extends keyof MessageEventTargetEventMap>(type: K, listener: (this: MessageEventTarget, ev: MessageEventTargetEventMap[K]) => any, options?: boolean | AddEventListenerOptions): void;
+    onmessageerror: ((this: MessageEventTarget<T>, ev: MessageEvent) => any) | null;
+    addEventListener<K extends keyof MessageEventTargetEventMap>(type: K, listener: (this: MessageEventTarget<T>, ev: MessageEventTargetEventMap[K]) => any, options?: boolean | AddEventListenerOptions): void;
     addEventListener(type: string, listener: EventListenerOrEventListenerObject, options?: boolean | AddEventListenerOptions): void;
-    removeEventListener<K extends keyof MessageEventTargetEventMap>(type: K, listener: (this: MessageEventTarget, ev: MessageEventTargetEventMap[K]) => any, options?: boolean | EventListenerOptions): void;
+    removeEventListener<K extends keyof MessageEventTargetEventMap>(type: K, listener: (this: MessageEventTarget<T>, ev: MessageEventTargetEventMap[K]) => any, options?: boolean | EventListenerOptions): void;
     removeEventListener(type: string, listener: EventListenerOrEventListenerObject, options?: boolean | EventListenerOptions): void;
 }
 
@@ -3669,7 +3669,7 @@ interface MessagePortEventMap extends MessageEventTargetEventMap {
  *
  * [MDN Reference](https://developer.mozilla.org/docs/Web/API/MessagePort)
  */
-interface MessagePort extends EventTarget, MessageEventTarget {
+interface MessagePort extends EventTarget, MessageEventTarget<MessagePort> {
     /**
      * Disconnects the port, so that it is no longer active.
      *
@@ -7841,8 +7841,6 @@ interface WindowOrWorkerGlobalScope {
 }
 
 interface WorkerEventMap extends AbstractWorkerEventMap, MessageEventTargetEventMap {
-    "message": MessageEvent;
-    "messageerror": MessageEvent;
 }
 
 /**
@@ -7850,7 +7848,7 @@ interface WorkerEventMap extends AbstractWorkerEventMap, MessageEventTargetEvent
  *
  * [MDN Reference](https://developer.mozilla.org/docs/Web/API/Worker)
  */
-interface Worker extends EventTarget, AbstractWorker, MessageEventTarget {
+interface Worker extends EventTarget, AbstractWorker, MessageEventTarget<Worker> {
     /**
      * Clones message and transmits it to worker's global environment. transfer can be passed as a list of objects that are to be transferred rather than cloned.
      *
diff --git a/baselines/ts5.5/audioworklet.generated.d.ts b/baselines/ts5.5/audioworklet.generated.d.ts
index 1d5a8086b..e23e869a6 100644
--- a/baselines/ts5.5/audioworklet.generated.d.ts
+++ b/baselines/ts5.5/audioworklet.generated.d.ts
@@ -682,14 +682,14 @@ interface MessageEventTargetEventMap {
     "messageerror": MessageEvent;
 }
 
-interface MessageEventTarget {
+interface MessageEventTarget<T> {
     /** [MDN Reference](https://developer.mozilla.org/docs/Web/API/DedicatedWorkerGlobalScope/message_event) */
-    onmessage: ((this: MessageEventTarget, ev: MessageEvent) => any) | null;
+    onmessage: ((this: MessageEventTarget<T>, ev: MessageEvent) => any) | null;
     /** [MDN Reference](https://developer.mozilla.org/docs/Web/API/DedicatedWorkerGlobalScope/messageerror_event) */
-    onmessageerror: ((this: MessageEventTarget, ev: MessageEvent) => any) | null;
-    addEventListener<K extends keyof MessageEventTargetEventMap>(type: K, listener: (this: MessageEventTarget, ev: MessageEventTargetEventMap[K]) => any, options?: boolean | AddEventListenerOptions): void;
+    onmessageerror: ((this: MessageEventTarget<T>, ev: MessageEvent) => any) | null;
+    addEventListener<K extends keyof MessageEventTargetEventMap>(type: K, listener: (this: MessageEventTarget<T>, ev: MessageEventTargetEventMap[K]) => any, options?: boolean | AddEventListenerOptions): void;
     addEventListener(type: string, listener: EventListenerOrEventListenerObject, options?: boolean | AddEventListenerOptions): void;
-    removeEventListener<K extends keyof MessageEventTargetEventMap>(type: K, listener: (this: MessageEventTarget, ev: MessageEventTargetEventMap[K]) => any, options?: boolean | EventListenerOptions): void;
+    removeEventListener<K extends keyof MessageEventTargetEventMap>(type: K, listener: (this: MessageEventTarget<T>, ev: MessageEventTargetEventMap[K]) => any, options?: boolean | EventListenerOptions): void;
     removeEventListener(type: string, listener: EventListenerOrEventListenerObject, options?: boolean | EventListenerOptions): void;
 }
 
@@ -703,7 +703,7 @@ interface MessagePortEventMap extends MessageEventTargetEventMap {
  *
  * [MDN Reference](https://developer.mozilla.org/docs/Web/API/MessagePort)
  */
-interface MessagePort extends EventTarget, MessageEventTarget {
+interface MessagePort extends EventTarget, MessageEventTarget<MessagePort> {
     /**
      * Disconnects the port, so that it is no longer active.
      *
diff --git a/baselines/ts5.5/dom.generated.d.ts b/baselines/ts5.5/dom.generated.d.ts
index d6a806977..0111bacf0 100644
--- a/baselines/ts5.5/dom.generated.d.ts
+++ b/baselines/ts5.5/dom.generated.d.ts
@@ -16369,14 +16369,14 @@ interface MessageEventTargetEventMap {
     "messageerror": MessageEvent;
 }
 
-interface MessageEventTarget {
+interface MessageEventTarget<T> {
     /** [MDN Reference](https://developer.mozilla.org/docs/Web/API/DedicatedWorkerGlobalScope/message_event) */
-    onmessage: ((this: MessageEventTarget, ev: MessageEvent) => any) | null;
+    onmessage: ((this: MessageEventTarget<T>, ev: MessageEvent) => any) | null;
     /** [MDN Reference](https://developer.mozilla.org/docs/Web/API/DedicatedWorkerGlobalScope/messageerror_event) */
-    onmessageerror: ((this: MessageEventTarget, ev: MessageEvent) => any) | null;
-    addEventListener<K extends keyof MessageEventTargetEventMap>(type: K, listener: (this: MessageEventTarget, ev: MessageEventTargetEventMap[K]) => any, options?: boolean | AddEventListenerOptions): void;
+    onmessageerror: ((this: MessageEventTarget<T>, ev: MessageEvent) => any) | null;
+    addEventListener<K extends keyof MessageEventTargetEventMap>(type: K, listener: (this: MessageEventTarget<T>, ev: MessageEventTargetEventMap[K]) => any, options?: boolean | AddEventListenerOptions): void;
     addEventListener(type: string, listener: EventListenerOrEventListenerObject, options?: boolean | AddEventListenerOptions): void;
-    removeEventListener<K extends keyof MessageEventTargetEventMap>(type: K, listener: (this: MessageEventTarget, ev: MessageEventTargetEventMap[K]) => any, options?: boolean | EventListenerOptions): void;
+    removeEventListener<K extends keyof MessageEventTargetEventMap>(type: K, listener: (this: MessageEventTarget<T>, ev: MessageEventTargetEventMap[K]) => any, options?: boolean | EventListenerOptions): void;
     removeEventListener(type: string, listener: EventListenerOrEventListenerObject, options?: boolean | EventListenerOptions): void;
 }
 
@@ -16390,7 +16390,7 @@ interface MessagePortEventMap extends MessageEventTargetEventMap {
  *
  * [MDN Reference](https://developer.mozilla.org/docs/Web/API/MessagePort)
  */
-interface MessagePort extends EventTarget, MessageEventTarget {
+interface MessagePort extends EventTarget, MessageEventTarget<MessagePort> {
     /**
      * Disconnects the port, so that it is no longer active.
      *
@@ -27237,8 +27237,6 @@ interface WindowSessionStorage {
 }
 
 interface WorkerEventMap extends AbstractWorkerEventMap, MessageEventTargetEventMap {
-    "message": MessageEvent;
-    "messageerror": MessageEvent;
 }
 
 /**
@@ -27246,7 +27244,7 @@ interface WorkerEventMap extends AbstractWorkerEventMap, MessageEventTargetEvent
  *
  * [MDN Reference](https://developer.mozilla.org/docs/Web/API/Worker)
  */
-interface Worker extends EventTarget, AbstractWorker, MessageEventTarget {
+interface Worker extends EventTarget, AbstractWorker, MessageEventTarget<Worker> {
     /**
      * Clones message and transmits it to worker's global environment. transfer can be passed as a list of objects that are to be transferred rather than cloned.
      *
diff --git a/baselines/ts5.5/serviceworker.generated.d.ts b/baselines/ts5.5/serviceworker.generated.d.ts
index f848ec0fd..30cda9881 100644
--- a/baselines/ts5.5/serviceworker.generated.d.ts
+++ b/baselines/ts5.5/serviceworker.generated.d.ts
@@ -3759,14 +3759,14 @@ interface MessageEventTargetEventMap {
     "messageerror": MessageEvent;
 }
 
-interface MessageEventTarget {
+interface MessageEventTarget<T> {
     /** [MDN Reference](https://developer.mozilla.org/docs/Web/API/DedicatedWorkerGlobalScope/message_event) */
-    onmessage: ((this: MessageEventTarget, ev: MessageEvent) => any) | null;
+    onmessage: ((this: MessageEventTarget<T>, ev: MessageEvent) => any) | null;
     /** [MDN Reference](https://developer.mozilla.org/docs/Web/API/DedicatedWorkerGlobalScope/messageerror_event) */
-    onmessageerror: ((this: MessageEventTarget, ev: MessageEvent) => any) | null;
-    addEventListener<K extends keyof MessageEventTargetEventMap>(type: K, listener: (this: MessageEventTarget, ev: MessageEventTargetEventMap[K]) => any, options?: boolean | AddEventListenerOptions): void;
+    onmessageerror: ((this: MessageEventTarget<T>, ev: MessageEvent) => any) | null;
+    addEventListener<K extends keyof MessageEventTargetEventMap>(type: K, listener: (this: MessageEventTarget<T>, ev: MessageEventTargetEventMap[K]) => any, options?: boolean | AddEventListenerOptions): void;
     addEventListener(type: string, listener: EventListenerOrEventListenerObject, options?: boolean | AddEventListenerOptions): void;
-    removeEventListener<K extends keyof MessageEventTargetEventMap>(type: K, listener: (this: MessageEventTarget, ev: MessageEventTargetEventMap[K]) => any, options?: boolean | EventListenerOptions): void;
+    removeEventListener<K extends keyof MessageEventTargetEventMap>(type: K, listener: (this: MessageEventTarget<T>, ev: MessageEventTargetEventMap[K]) => any, options?: boolean | EventListenerOptions): void;
     removeEventListener(type: string, listener: EventListenerOrEventListenerObject, options?: boolean | EventListenerOptions): void;
 }
 
@@ -3780,7 +3780,7 @@ interface MessagePortEventMap extends MessageEventTargetEventMap {
  *
  * [MDN Reference](https://developer.mozilla.org/docs/Web/API/MessagePort)
  */
-interface MessagePort extends EventTarget, MessageEventTarget {
+interface MessagePort extends EventTarget, MessageEventTarget<MessagePort> {
     /**
      * Disconnects the port, so that it is no longer active.
      *
diff --git a/baselines/ts5.5/sharedworker.generated.d.ts b/baselines/ts5.5/sharedworker.generated.d.ts
index f2bb37e7a..9068ec8e5 100644
--- a/baselines/ts5.5/sharedworker.generated.d.ts
+++ b/baselines/ts5.5/sharedworker.generated.d.ts
@@ -3648,14 +3648,14 @@ interface MessageEventTargetEventMap {
     "messageerror": MessageEvent;
 }
 
-interface MessageEventTarget {
+interface MessageEventTarget<T> {
     /** [MDN Reference](https://developer.mozilla.org/docs/Web/API/DedicatedWorkerGlobalScope/message_event) */
-    onmessage: ((this: MessageEventTarget, ev: MessageEvent) => any) | null;
+    onmessage: ((this: MessageEventTarget<T>, ev: MessageEvent) => any) | null;
     /** [MDN Reference](https://developer.mozilla.org/docs/Web/API/DedicatedWorkerGlobalScope/messageerror_event) */
-    onmessageerror: ((this: MessageEventTarget, ev: MessageEvent) => any) | null;
-    addEventListener<K extends keyof MessageEventTargetEventMap>(type: K, listener: (this: MessageEventTarget, ev: MessageEventTargetEventMap[K]) => any, options?: boolean | AddEventListenerOptions): void;
+    onmessageerror: ((this: MessageEventTarget<T>, ev: MessageEvent) => any) | null;
+    addEventListener<K extends keyof MessageEventTargetEventMap>(type: K, listener: (this: MessageEventTarget<T>, ev: MessageEventTargetEventMap[K]) => any, options?: boolean | AddEventListenerOptions): void;
     addEventListener(type: string, listener: EventListenerOrEventListenerObject, options?: boolean | AddEventListenerOptions): void;
-    removeEventListener<K extends keyof MessageEventTargetEventMap>(type: K, listener: (this: MessageEventTarget, ev: MessageEventTargetEventMap[K]) => any, options?: boolean | EventListenerOptions): void;
+    removeEventListener<K extends keyof MessageEventTargetEventMap>(type: K, listener: (this: MessageEventTarget<T>, ev: MessageEventTargetEventMap[K]) => any, options?: boolean | EventListenerOptions): void;
     removeEventListener(type: string, listener: EventListenerOrEventListenerObject, options?: boolean | EventListenerOptions): void;
 }
 
@@ -3669,7 +3669,7 @@ interface MessagePortEventMap extends MessageEventTargetEventMap {
  *
  * [MDN Reference](https://developer.mozilla.org/docs/Web/API/MessagePort)
  */
-interface MessagePort extends EventTarget, MessageEventTarget {
+interface MessagePort extends EventTarget, MessageEventTarget<MessagePort> {
     /**
      * Disconnects the port, so that it is no longer active.
      *
@@ -7841,8 +7841,6 @@ interface WindowOrWorkerGlobalScope {
 }
 
 interface WorkerEventMap extends AbstractWorkerEventMap, MessageEventTargetEventMap {
-    "message": MessageEvent;
-    "messageerror": MessageEvent;
 }
 
 /**
@@ -7850,7 +7848,7 @@ interface WorkerEventMap extends AbstractWorkerEventMap, MessageEventTargetEvent
  *
  * [MDN Reference](https://developer.mozilla.org/docs/Web/API/Worker)
  */
-interface Worker extends EventTarget, AbstractWorker, MessageEventTarget {
+interface Worker extends EventTarget, AbstractWorker, MessageEventTarget<Worker> {
     /**
      * Clones message and transmits it to worker's global environment. transfer can be passed as a list of objects that are to be transferred rather than cloned.
      *
diff --git a/baselines/ts5.5/webworker.generated.d.ts b/baselines/ts5.5/webworker.generated.d.ts
index 37c8fd5ca..e2b2b0b76 100644
--- a/baselines/ts5.5/webworker.generated.d.ts
+++ b/baselines/ts5.5/webworker.generated.d.ts
@@ -2497,7 +2497,7 @@ interface DedicatedWorkerGlobalScopeEventMap extends WorkerGlobalScopeEventMap,
  *
  * [MDN Reference](https://developer.mozilla.org/docs/Web/API/DedicatedWorkerGlobalScope)
  */
-interface DedicatedWorkerGlobalScope extends WorkerGlobalScope, AnimationFrameProvider, MessageEventTarget {
+interface DedicatedWorkerGlobalScope extends WorkerGlobalScope, AnimationFrameProvider, MessageEventTarget<DedicatedWorkerGlobalScope> {
     /**
      * Returns dedicatedWorkerGlobal's name, i.e. the value given to the Worker constructor. Primarily useful for debugging.
      *
@@ -4333,14 +4333,14 @@ interface MessageEventTargetEventMap {
     "messageerror": MessageEvent;
 }
 
-interface MessageEventTarget {
+interface MessageEventTarget<T> {
     /** [MDN Reference](https://developer.mozilla.org/docs/Web/API/DedicatedWorkerGlobalScope/message_event) */
-    onmessage: ((this: MessageEventTarget, ev: MessageEvent) => any) | null;
+    onmessage: ((this: MessageEventTarget<T>, ev: MessageEvent) => any) | null;
     /** [MDN Reference](https://developer.mozilla.org/docs/Web/API/DedicatedWorkerGlobalScope/messageerror_event) */
-    onmessageerror: ((this: MessageEventTarget, ev: MessageEvent) => any) | null;
-    addEventListener<K extends keyof MessageEventTargetEventMap>(type: K, listener: (this: MessageEventTarget, ev: MessageEventTargetEventMap[K]) => any, options?: boolean | AddEventListenerOptions): void;
+    onmessageerror: ((this: MessageEventTarget<T>, ev: MessageEvent) => any) | null;
+    addEventListener<K extends keyof MessageEventTargetEventMap>(type: K, listener: (this: MessageEventTarget<T>, ev: MessageEventTargetEventMap[K]) => any, options?: boolean | AddEventListenerOptions): void;
     addEventListener(type: string, listener: EventListenerOrEventListenerObject, options?: boolean | AddEventListenerOptions): void;
-    removeEventListener<K extends keyof MessageEventTargetEventMap>(type: K, listener: (this: MessageEventTarget, ev: MessageEventTargetEventMap[K]) => any, options?: boolean | EventListenerOptions): void;
+    removeEventListener<K extends keyof MessageEventTargetEventMap>(type: K, listener: (this: MessageEventTarget<T>, ev: MessageEventTargetEventMap[K]) => any, options?: boolean | EventListenerOptions): void;
     removeEventListener(type: string, listener: EventListenerOrEventListenerObject, options?: boolean | EventListenerOptions): void;
 }
 
@@ -4354,7 +4354,7 @@ interface MessagePortEventMap extends MessageEventTargetEventMap {
  *
  * [MDN Reference](https://developer.mozilla.org/docs/Web/API/MessagePort)
  */
-interface MessagePort extends EventTarget, MessageEventTarget {
+interface MessagePort extends EventTarget, MessageEventTarget<MessagePort> {
     /**
      * Disconnects the port, so that it is no longer active.
      *
@@ -8920,8 +8920,6 @@ interface WindowOrWorkerGlobalScope {
 }
 
 interface WorkerEventMap extends AbstractWorkerEventMap, MessageEventTargetEventMap {
-    "message": MessageEvent;
-    "messageerror": MessageEvent;
 }
 
 /**
@@ -8929,7 +8927,7 @@ interface WorkerEventMap extends AbstractWorkerEventMap, MessageEventTargetEvent
  *
  * [MDN Reference](https://developer.mozilla.org/docs/Web/API/Worker)
  */
-interface Worker extends EventTarget, AbstractWorker, MessageEventTarget {
+interface Worker extends EventTarget, AbstractWorker, MessageEventTarget<Worker> {
     /**
      * Clones message and transmits it to worker's global environment. transfer can be passed as a list of objects that are to be transferred rather than cloned.
      *
diff --git a/baselines/webworker.generated.d.ts b/baselines/webworker.generated.d.ts
index 37c8fd5ca..e2b2b0b76 100644
--- a/baselines/webworker.generated.d.ts
+++ b/baselines/webworker.generated.d.ts
@@ -2497,7 +2497,7 @@ interface DedicatedWorkerGlobalScopeEventMap extends WorkerGlobalScopeEventMap,
  *
  * [MDN Reference](https://developer.mozilla.org/docs/Web/API/DedicatedWorkerGlobalScope)
  */
-interface DedicatedWorkerGlobalScope extends WorkerGlobalScope, AnimationFrameProvider, MessageEventTarget {
+interface DedicatedWorkerGlobalScope extends WorkerGlobalScope, AnimationFrameProvider, MessageEventTarget<DedicatedWorkerGlobalScope> {
     /**
      * Returns dedicatedWorkerGlobal's name, i.e. the value given to the Worker constructor. Primarily useful for debugging.
      *
@@ -4333,14 +4333,14 @@ interface MessageEventTargetEventMap {
     "messageerror": MessageEvent;
 }
 
-interface MessageEventTarget {
+interface MessageEventTarget<T> {
     /** [MDN Reference](https://developer.mozilla.org/docs/Web/API/DedicatedWorkerGlobalScope/message_event) */
-    onmessage: ((this: MessageEventTarget, ev: MessageEvent) => any) | null;
+    onmessage: ((this: MessageEventTarget<T>, ev: MessageEvent) => any) | null;
     /** [MDN Reference](https://developer.mozilla.org/docs/Web/API/DedicatedWorkerGlobalScope/messageerror_event) */
-    onmessageerror: ((this: MessageEventTarget, ev: MessageEvent) => any) | null;
-    addEventListener<K extends keyof MessageEventTargetEventMap>(type: K, listener: (this: MessageEventTarget, ev: MessageEventTargetEventMap[K]) => any, options?: boolean | AddEventListenerOptions): void;
+    onmessageerror: ((this: MessageEventTarget<T>, ev: MessageEvent) => any) | null;
+    addEventListener<K extends keyof MessageEventTargetEventMap>(type: K, listener: (this: MessageEventTarget<T>, ev: MessageEventTargetEventMap[K]) => any, options?: boolean | AddEventListenerOptions): void;
     addEventListener(type: string, listener: EventListenerOrEventListenerObject, options?: boolean | AddEventListenerOptions): void;
-    removeEventListener<K extends keyof MessageEventTargetEventMap>(type: K, listener: (this: MessageEventTarget, ev: MessageEventTargetEventMap[K]) => any, options?: boolean | EventListenerOptions): void;
+    removeEventListener<K extends keyof MessageEventTargetEventMap>(type: K, listener: (this: MessageEventTarget<T>, ev: MessageEventTargetEventMap[K]) => any, options?: boolean | EventListenerOptions): void;
     removeEventListener(type: string, listener: EventListenerOrEventListenerObject, options?: boolean | EventListenerOptions): void;
 }
 
@@ -4354,7 +4354,7 @@ interface MessagePortEventMap extends MessageEventTargetEventMap {
  *
  * [MDN Reference](https://developer.mozilla.org/docs/Web/API/MessagePort)
  */
-interface MessagePort extends EventTarget, MessageEventTarget {
+interface MessagePort extends EventTarget, MessageEventTarget<MessagePort> {
     /**
      * Disconnects the port, so that it is no longer active.
      *
@@ -8920,8 +8920,6 @@ interface WindowOrWorkerGlobalScope {
 }
 
 interface WorkerEventMap extends AbstractWorkerEventMap, MessageEventTargetEventMap {
-    "message": MessageEvent;
-    "messageerror": MessageEvent;
 }
 
 /**
@@ -8929,7 +8927,7 @@ interface WorkerEventMap extends AbstractWorkerEventMap, MessageEventTargetEvent
  *
  * [MDN Reference](https://developer.mozilla.org/docs/Web/API/Worker)
  */
-interface Worker extends EventTarget, AbstractWorker, MessageEventTarget {
+interface Worker extends EventTarget, AbstractWorker, MessageEventTarget<Worker> {
     /**
      * Clones message and transmits it to worker's global environment. transfer can be passed as a list of objects that are to be transferred rather than cloned.
      *
diff --git a/inputfiles/overridingTypes.jsonc b/inputfiles/overridingTypes.jsonc
index 35d52d3dc..c319aa2c3 100644
--- a/inputfiles/overridingTypes.jsonc
+++ b/inputfiles/overridingTypes.jsonc
@@ -2,6 +2,11 @@
     "mixins": {
         "mixin": {
             "MessageEventTarget": {
+                "typeParameters": [
+                    {
+                        "name": "T"
+                    }
+                ],
                 "events": {
                     "event": [
                         {
@@ -2521,6 +2526,7 @@
                 ]
             },
             "Worker": {
+                "overrideImplements": ["AbstractWorker", "MessageEventTarget<Worker>"],
                 "methods": {
                     "method": {
                         "postMessage": {
@@ -2536,18 +2542,6 @@
                             }
                         }
                     }
-                },
-                "events": {
-                    "event": [
-                        {
-                            "name": "message",
-                            "type": "MessageEvent"
-                        },
-                        {
-                            "name": "messageerror",
-                            "type": "MessageEvent"
-                        }
-                    ]
                 }
             },
             "Crypto": {
@@ -2626,6 +2620,7 @@
                 }
             },
             "MessagePort": {
+                "overrideImplements": ["MessageEventTarget<MessagePort>"],
                 "methods": {
                     "method": {
                         "postMessage": {
@@ -2674,6 +2669,7 @@
                 }
             },
             "DedicatedWorkerGlobalScope": {
+                "overrideImplements": ["AnimationFrameProvider", "MessageEventTarget<DedicatedWorkerGlobalScope>"],
                 "methods": {
                     "method": {
                         "postMessage": {
diff --git a/src/build/emitter.ts b/src/build/emitter.ts
index 0760d7dd7..57d5689ed 100644
--- a/src/build/emitter.ts
+++ b/src/build/emitter.ts
@@ -1227,10 +1227,9 @@ export function emitWebIdl(
     );
 
     const finalExtends = [i.extends || "Object"]
-      .concat(getImplementList(i.name))
+      .concat(i.overrideImplements ?? getImplementList(i.name))
       .filter((i) => i !== "Object")
       .map(processIName);
-
     if (finalExtends.length) {
       printer.print(` extends ${assertUnique(finalExtends).join(", ")}`);
     }
diff --git a/src/build/types.d.ts b/src/build/types.d.ts
index b3c68a68f..a5257eaa2 100644
--- a/src/build/types.d.ts
+++ b/src/build/types.d.ts
@@ -169,6 +169,7 @@ export interface Interface {
   };
   constructor?: Constructor;
   implements?: string[];
+  overrideImplements?: string[];
   anonymousMethods?: {
     method: AnonymousMethod[];
   };