diff --git a/GDJS/Runtime/InGameEditor/InGameEditor.tsx b/GDJS/Runtime/InGameEditor/InGameEditor.tsx
index ebfecdaaba11..bfeceb8b0c2c 100644
--- a/GDJS/Runtime/InGameEditor/InGameEditor.tsx
+++ b/GDJS/Runtime/InGameEditor/InGameEditor.tsx
@@ -366,13 +366,17 @@ namespace gdjs {
   };
 
   let hasWindowFocus = true;
+  // References for cleanup
+  const _onWindowFocus = () => {
+    hasWindowFocus = true;
+  };
+  const _onWindowBlur = () => {
+    hasWindowFocus = false;
+  };
+
   if (typeof window !== 'undefined') {
-    window.addEventListener('focus', () => {
-      hasWindowFocus = true;
-    });
-    window.addEventListener('blur', () => {
-      hasWindowFocus = false;
-    });
+    window.addEventListener('focus', _onWindowFocus);
+    window.addEventListener('blur', _onWindowBlur);
   }
 
   function isDefined<T>(value: T | null | undefined): value is NonNullable<T> {
@@ -962,6 +966,10 @@ namespace gdjs {
         this._unregisterContextLostListener();
         this._unregisterContextLostListener = null;
       }
+      if (typeof window !== 'undefined') {
+        window.removeEventListener('focus', _onWindowFocus);
+        window.removeEventListener('blur', _onWindowBlur);
+      }
     }
 
     private _applyInGameEditorSettings() {
diff --git a/GDJS/Runtime/debugger-client/abstract-debugger-client.ts b/GDJS/Runtime/debugger-client/abstract-debugger-client.ts
index 3930778ec4cb..adfe4c6e480c 100644
--- a/GDJS/Runtime/debugger-client/abstract-debugger-client.ts
+++ b/GDJS/Runtime/debugger-client/abstract-debugger-client.ts
@@ -499,6 +499,8 @@ namespace gdjs {
       }
     }
 
+    abstract dispose(): void;
+
     /**
      * Should be re-implemented by derived class to send a stringified message object
      * to the debugger server.
diff --git a/GDJS/Runtime/debugger-client/minimal-debugger-client.ts b/GDJS/Runtime/debugger-client/minimal-debugger-client.ts
index 2da441a5fbb2..4a5e82c93f2d 100644
--- a/GDJS/Runtime/debugger-client/minimal-debugger-client.ts
+++ b/GDJS/Runtime/debugger-client/minimal-debugger-client.ts
@@ -8,6 +8,8 @@ namespace gdjs {
       super(runtimeGame);
     }
 
+    dispose(): void {}
+
     protected _sendMessage(message: string) {}
   }
 
diff --git a/GDJS/Runtime/debugger-client/websocket-debugger-client.ts b/GDJS/Runtime/debugger-client/websocket-debugger-client.ts
index a6462acad739..7af40df5a111 100644
--- a/GDJS/Runtime/debugger-client/websocket-debugger-client.ts
+++ b/GDJS/Runtime/debugger-client/websocket-debugger-client.ts
@@ -86,6 +86,13 @@ namespace gdjs {
     }
 
     private hasLoggedError: boolean = false;
+
+    dispose(): void {
+      if (this._ws) {
+        this._ws.close();
+      }
+    }
+
     protected _sendMessage(message: string) {
       if (!this._ws) {
         // The error can be logged only once, since logger.warn will call this function again,
diff --git a/GDJS/Runtime/debugger-client/window-message-debugger-client.ts b/GDJS/Runtime/debugger-client/window-message-debugger-client.ts
index 5c35a9004427..c764daac4fce 100644
--- a/GDJS/Runtime/debugger-client/window-message-debugger-client.ts
+++ b/GDJS/Runtime/debugger-client/window-message-debugger-client.ts
@@ -8,6 +8,10 @@ namespace gdjs {
    */
   export class WindowMessageDebuggerClient extends gdjs.AbstractDebuggerClient {
     _opener: Window | null = null;
+    private _onWindowMessage = (event: MessageEvent) => {
+      const data = event.data;
+      this.handleCommand(data);
+    };
 
     constructor(runtimeGame: RuntimeGame) {
       super(runtimeGame);
@@ -24,10 +28,11 @@ namespace gdjs {
         return;
       }
 
-      window.addEventListener('message', (event) => {
-        const data = event.data;
-        this.handleCommand(data);
-      });
+      window.addEventListener('message', this._onWindowMessage);
+    }
+
+    dispose() {
+      window.removeEventListener('message', this._onWindowMessage);
     }
 
     protected _sendMessage(message: string) {
diff --git a/GDJS/Runtime/runtimegame.ts b/GDJS/Runtime/runtimegame.ts
index be92cd47d24e..df1d29ce772f 100644
--- a/GDJS/Runtime/runtimegame.ts
+++ b/GDJS/Runtime/runtimegame.ts
@@ -1270,6 +1270,9 @@ namespace gdjs {
       if (this._inGameEditor) {
         this._inGameEditor.dispose();
       }
+      if (this._debuggerClient) {
+        this._debuggerClient.dispose();
+      }
       this._renderer.stopGameLoop();
       this._sceneStack.dispose();
       this._renderer.dispose(removeCanvas);