diff --git a/baselines/audioworklet.generated.d.ts b/baselines/audioworklet.generated.d.ts
index ae1874c12..1d5a8086b 100644
--- a/baselines/audioworklet.generated.d.ts
+++ b/baselines/audioworklet.generated.d.ts
@@ -678,15 +678,15 @@ declare var MessageEvent: {
 };
 
 interface MessageEventTargetEventMap {
-    "message": Event;
-    "messageerror": Event;
+    "message": MessageEvent;
+    "messageerror": MessageEvent;
 }
 
 interface MessageEventTarget {
     /** [MDN Reference](https://developer.mozilla.org/docs/Web/API/DedicatedWorkerGlobalScope/message_event) */
-    onmessage: ((this: MessageEventTarget, ev: Event) => any) | null;
+    onmessage: ((this: MessageEventTarget, ev: MessageEvent) => any) | null;
     /** [MDN Reference](https://developer.mozilla.org/docs/Web/API/DedicatedWorkerGlobalScope/messageerror_event) */
-    onmessageerror: ((this: MessageEventTarget, ev: Event) => any) | null;
+    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;
     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;
diff --git a/baselines/dom.generated.d.ts b/baselines/dom.generated.d.ts
index b78862550..bcae88127 100644
--- a/baselines/dom.generated.d.ts
+++ b/baselines/dom.generated.d.ts
@@ -16385,15 +16385,15 @@ declare var MessageEvent: {
 };
 
 interface MessageEventTargetEventMap {
-    "message": Event;
-    "messageerror": Event;
+    "message": MessageEvent;
+    "messageerror": MessageEvent;
 }
 
 interface MessageEventTarget {
     /** [MDN Reference](https://developer.mozilla.org/docs/Web/API/DedicatedWorkerGlobalScope/message_event) */
-    onmessage: ((this: MessageEventTarget, ev: Event) => any) | null;
+    onmessage: ((this: MessageEventTarget, ev: MessageEvent) => any) | null;
     /** [MDN Reference](https://developer.mozilla.org/docs/Web/API/DedicatedWorkerGlobalScope/messageerror_event) */
-    onmessageerror: ((this: MessageEventTarget, ev: Event) => any) | null;
+    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;
     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;
diff --git a/baselines/serviceworker.generated.d.ts b/baselines/serviceworker.generated.d.ts
index 13b1cc7d9..f848ec0fd 100644
--- a/baselines/serviceworker.generated.d.ts
+++ b/baselines/serviceworker.generated.d.ts
@@ -3755,15 +3755,15 @@ declare var MessageEvent: {
 };
 
 interface MessageEventTargetEventMap {
-    "message": Event;
-    "messageerror": Event;
+    "message": MessageEvent;
+    "messageerror": MessageEvent;
 }
 
 interface MessageEventTarget {
     /** [MDN Reference](https://developer.mozilla.org/docs/Web/API/DedicatedWorkerGlobalScope/message_event) */
-    onmessage: ((this: MessageEventTarget, ev: Event) => any) | null;
+    onmessage: ((this: MessageEventTarget, ev: MessageEvent) => any) | null;
     /** [MDN Reference](https://developer.mozilla.org/docs/Web/API/DedicatedWorkerGlobalScope/messageerror_event) */
-    onmessageerror: ((this: MessageEventTarget, ev: Event) => any) | null;
+    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;
     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;
diff --git a/baselines/sharedworker.generated.d.ts b/baselines/sharedworker.generated.d.ts
index 43efdf8d1..f2bb37e7a 100644
--- a/baselines/sharedworker.generated.d.ts
+++ b/baselines/sharedworker.generated.d.ts
@@ -3644,15 +3644,15 @@ declare var MessageEvent: {
 };
 
 interface MessageEventTargetEventMap {
-    "message": Event;
-    "messageerror": Event;
+    "message": MessageEvent;
+    "messageerror": MessageEvent;
 }
 
 interface MessageEventTarget {
     /** [MDN Reference](https://developer.mozilla.org/docs/Web/API/DedicatedWorkerGlobalScope/message_event) */
-    onmessage: ((this: MessageEventTarget, ev: Event) => any) | null;
+    onmessage: ((this: MessageEventTarget, ev: MessageEvent) => any) | null;
     /** [MDN Reference](https://developer.mozilla.org/docs/Web/API/DedicatedWorkerGlobalScope/messageerror_event) */
-    onmessageerror: ((this: MessageEventTarget, ev: Event) => any) | null;
+    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;
     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;
diff --git a/baselines/ts5.5/audioworklet.generated.d.ts b/baselines/ts5.5/audioworklet.generated.d.ts
index ae1874c12..1d5a8086b 100644
--- a/baselines/ts5.5/audioworklet.generated.d.ts
+++ b/baselines/ts5.5/audioworklet.generated.d.ts
@@ -678,15 +678,15 @@ declare var MessageEvent: {
 };
 
 interface MessageEventTargetEventMap {
-    "message": Event;
-    "messageerror": Event;
+    "message": MessageEvent;
+    "messageerror": MessageEvent;
 }
 
 interface MessageEventTarget {
     /** [MDN Reference](https://developer.mozilla.org/docs/Web/API/DedicatedWorkerGlobalScope/message_event) */
-    onmessage: ((this: MessageEventTarget, ev: Event) => any) | null;
+    onmessage: ((this: MessageEventTarget, ev: MessageEvent) => any) | null;
     /** [MDN Reference](https://developer.mozilla.org/docs/Web/API/DedicatedWorkerGlobalScope/messageerror_event) */
-    onmessageerror: ((this: MessageEventTarget, ev: Event) => any) | null;
+    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;
     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;
diff --git a/baselines/ts5.5/dom.generated.d.ts b/baselines/ts5.5/dom.generated.d.ts
index 1a543ef33..d6a806977 100644
--- a/baselines/ts5.5/dom.generated.d.ts
+++ b/baselines/ts5.5/dom.generated.d.ts
@@ -16365,15 +16365,15 @@ declare var MessageEvent: {
 };
 
 interface MessageEventTargetEventMap {
-    "message": Event;
-    "messageerror": Event;
+    "message": MessageEvent;
+    "messageerror": MessageEvent;
 }
 
 interface MessageEventTarget {
     /** [MDN Reference](https://developer.mozilla.org/docs/Web/API/DedicatedWorkerGlobalScope/message_event) */
-    onmessage: ((this: MessageEventTarget, ev: Event) => any) | null;
+    onmessage: ((this: MessageEventTarget, ev: MessageEvent) => any) | null;
     /** [MDN Reference](https://developer.mozilla.org/docs/Web/API/DedicatedWorkerGlobalScope/messageerror_event) */
-    onmessageerror: ((this: MessageEventTarget, ev: Event) => any) | null;
+    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;
     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;
diff --git a/baselines/ts5.5/serviceworker.generated.d.ts b/baselines/ts5.5/serviceworker.generated.d.ts
index 13b1cc7d9..f848ec0fd 100644
--- a/baselines/ts5.5/serviceworker.generated.d.ts
+++ b/baselines/ts5.5/serviceworker.generated.d.ts
@@ -3755,15 +3755,15 @@ declare var MessageEvent: {
 };
 
 interface MessageEventTargetEventMap {
-    "message": Event;
-    "messageerror": Event;
+    "message": MessageEvent;
+    "messageerror": MessageEvent;
 }
 
 interface MessageEventTarget {
     /** [MDN Reference](https://developer.mozilla.org/docs/Web/API/DedicatedWorkerGlobalScope/message_event) */
-    onmessage: ((this: MessageEventTarget, ev: Event) => any) | null;
+    onmessage: ((this: MessageEventTarget, ev: MessageEvent) => any) | null;
     /** [MDN Reference](https://developer.mozilla.org/docs/Web/API/DedicatedWorkerGlobalScope/messageerror_event) */
-    onmessageerror: ((this: MessageEventTarget, ev: Event) => any) | null;
+    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;
     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;
diff --git a/baselines/ts5.5/sharedworker.generated.d.ts b/baselines/ts5.5/sharedworker.generated.d.ts
index 43efdf8d1..f2bb37e7a 100644
--- a/baselines/ts5.5/sharedworker.generated.d.ts
+++ b/baselines/ts5.5/sharedworker.generated.d.ts
@@ -3644,15 +3644,15 @@ declare var MessageEvent: {
 };
 
 interface MessageEventTargetEventMap {
-    "message": Event;
-    "messageerror": Event;
+    "message": MessageEvent;
+    "messageerror": MessageEvent;
 }
 
 interface MessageEventTarget {
     /** [MDN Reference](https://developer.mozilla.org/docs/Web/API/DedicatedWorkerGlobalScope/message_event) */
-    onmessage: ((this: MessageEventTarget, ev: Event) => any) | null;
+    onmessage: ((this: MessageEventTarget, ev: MessageEvent) => any) | null;
     /** [MDN Reference](https://developer.mozilla.org/docs/Web/API/DedicatedWorkerGlobalScope/messageerror_event) */
-    onmessageerror: ((this: MessageEventTarget, ev: Event) => any) | null;
+    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;
     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;
diff --git a/baselines/ts5.5/webworker.generated.d.ts b/baselines/ts5.5/webworker.generated.d.ts
index 0edb041dc..37c8fd5ca 100644
--- a/baselines/ts5.5/webworker.generated.d.ts
+++ b/baselines/ts5.5/webworker.generated.d.ts
@@ -4329,15 +4329,15 @@ declare var MessageEvent: {
 };
 
 interface MessageEventTargetEventMap {
-    "message": Event;
-    "messageerror": Event;
+    "message": MessageEvent;
+    "messageerror": MessageEvent;
 }
 
 interface MessageEventTarget {
     /** [MDN Reference](https://developer.mozilla.org/docs/Web/API/DedicatedWorkerGlobalScope/message_event) */
-    onmessage: ((this: MessageEventTarget, ev: Event) => any) | null;
+    onmessage: ((this: MessageEventTarget, ev: MessageEvent) => any) | null;
     /** [MDN Reference](https://developer.mozilla.org/docs/Web/API/DedicatedWorkerGlobalScope/messageerror_event) */
-    onmessageerror: ((this: MessageEventTarget, ev: Event) => any) | null;
+    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;
     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;
@@ -9732,9 +9732,9 @@ declare function cancelAnimationFrame(handle: number): void;
 /** [MDN Reference](https://developer.mozilla.org/docs/Web/API/DedicatedWorkerGlobalScope/requestAnimationFrame) */
 declare function requestAnimationFrame(callback: FrameRequestCallback): number;
 /** [MDN Reference](https://developer.mozilla.org/docs/Web/API/DedicatedWorkerGlobalScope/message_event) */
-declare var onmessage: ((this: DedicatedWorkerGlobalScope, ev: Event) => any) | null;
+declare var onmessage: ((this: DedicatedWorkerGlobalScope, ev: MessageEvent) => any) | null;
 /** [MDN Reference](https://developer.mozilla.org/docs/Web/API/DedicatedWorkerGlobalScope/messageerror_event) */
-declare var onmessageerror: ((this: DedicatedWorkerGlobalScope, ev: Event) => any) | null;
+declare var onmessageerror: ((this: DedicatedWorkerGlobalScope, ev: MessageEvent) => any) | null;
 declare function addEventListener<K extends keyof DedicatedWorkerGlobalScopeEventMap>(type: K, listener: (this: DedicatedWorkerGlobalScope, ev: DedicatedWorkerGlobalScopeEventMap[K]) => any, options?: boolean | AddEventListenerOptions): void;
 declare function addEventListener(type: string, listener: EventListenerOrEventListenerObject, options?: boolean | AddEventListenerOptions): void;
 declare function removeEventListener<K extends keyof DedicatedWorkerGlobalScopeEventMap>(type: K, listener: (this: DedicatedWorkerGlobalScope, ev: DedicatedWorkerGlobalScopeEventMap[K]) => any, options?: boolean | EventListenerOptions): void;
diff --git a/baselines/webworker.generated.d.ts b/baselines/webworker.generated.d.ts
index 0edb041dc..37c8fd5ca 100644
--- a/baselines/webworker.generated.d.ts
+++ b/baselines/webworker.generated.d.ts
@@ -4329,15 +4329,15 @@ declare var MessageEvent: {
 };
 
 interface MessageEventTargetEventMap {
-    "message": Event;
-    "messageerror": Event;
+    "message": MessageEvent;
+    "messageerror": MessageEvent;
 }
 
 interface MessageEventTarget {
     /** [MDN Reference](https://developer.mozilla.org/docs/Web/API/DedicatedWorkerGlobalScope/message_event) */
-    onmessage: ((this: MessageEventTarget, ev: Event) => any) | null;
+    onmessage: ((this: MessageEventTarget, ev: MessageEvent) => any) | null;
     /** [MDN Reference](https://developer.mozilla.org/docs/Web/API/DedicatedWorkerGlobalScope/messageerror_event) */
-    onmessageerror: ((this: MessageEventTarget, ev: Event) => any) | null;
+    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;
     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;
@@ -9732,9 +9732,9 @@ declare function cancelAnimationFrame(handle: number): void;
 /** [MDN Reference](https://developer.mozilla.org/docs/Web/API/DedicatedWorkerGlobalScope/requestAnimationFrame) */
 declare function requestAnimationFrame(callback: FrameRequestCallback): number;
 /** [MDN Reference](https://developer.mozilla.org/docs/Web/API/DedicatedWorkerGlobalScope/message_event) */
-declare var onmessage: ((this: DedicatedWorkerGlobalScope, ev: Event) => any) | null;
+declare var onmessage: ((this: DedicatedWorkerGlobalScope, ev: MessageEvent) => any) | null;
 /** [MDN Reference](https://developer.mozilla.org/docs/Web/API/DedicatedWorkerGlobalScope/messageerror_event) */
-declare var onmessageerror: ((this: DedicatedWorkerGlobalScope, ev: Event) => any) | null;
+declare var onmessageerror: ((this: DedicatedWorkerGlobalScope, ev: MessageEvent) => any) | null;
 declare function addEventListener<K extends keyof DedicatedWorkerGlobalScopeEventMap>(type: K, listener: (this: DedicatedWorkerGlobalScope, ev: DedicatedWorkerGlobalScopeEventMap[K]) => any, options?: boolean | AddEventListenerOptions): void;
 declare function addEventListener(type: string, listener: EventListenerOrEventListenerObject, options?: boolean | AddEventListenerOptions): void;
 declare function removeEventListener<K extends keyof DedicatedWorkerGlobalScopeEventMap>(type: K, listener: (this: DedicatedWorkerGlobalScope, ev: DedicatedWorkerGlobalScopeEventMap[K]) => any, options?: boolean | EventListenerOptions): void;
diff --git a/inputfiles/overridingTypes.jsonc b/inputfiles/overridingTypes.jsonc
index ccd85731b..35d52d3dc 100644
--- a/inputfiles/overridingTypes.jsonc
+++ b/inputfiles/overridingTypes.jsonc
@@ -1,6 +1,20 @@
 {
     "mixins": {
         "mixin": {
+            "MessageEventTarget": {
+                "events": {
+                    "event": [
+                        {
+                            "name": "message",
+                            "type": "MessageEvent"
+                        },
+                        {
+                            "name": "messageerror",
+                            "type": "MessageEvent"
+                        }
+                    ]
+                }
+            },
             "ChildNode": {
                 "extends": "Node"
             },