diff --git a/packages/playwright-core/src/server/bidi/bidiBrowser.ts b/packages/playwright-core/src/server/bidi/bidiBrowser.ts
index 27330f09d9..30c1cdb1c4 100644
--- a/packages/playwright-core/src/server/bidi/bidiBrowser.ts
+++ b/packages/playwright-core/src/server/bidi/bidiBrowser.ts
@@ -209,6 +209,7 @@ export class BidiBrowserContext extends BrowserContext {
   declare readonly _browser: BidiBrowser;
   private _originToPermissions = new Map<string, string[]>();
   private _blockingPageCreations: Set<Promise<unknown>> = new Set();
+  private _initScriptIds = new Map<InitScript, string>();
 
   constructor(browser: BidiBrowser, browserContextId: string | undefined, options: types.BrowserContextOptions) {
     super(browser, options, browserContextId);
@@ -371,11 +372,18 @@ export class BidiBrowserContext extends BrowserContext {
       functionDeclaration: `() => { return ${initScript.source} }`,
       userContexts: [this._browserContextId || 'default'],
     });
-    initScript.auxData = script;
+    this._initScriptIds.set(initScript, script);
   }
 
   async doRemoveInitScripts(initScripts: InitScript[]) {
-    await Promise.all(initScripts.map(script => this._browser._browserSession.send('script.removePreloadScript', { script: script.auxData })));
+    const ids: string[] = [];
+    for (const script of initScripts) {
+      const id = this._initScriptIds.get(script);
+      if (id)
+        ids.push(id);
+      this._initScriptIds.delete(script);
+    }
+    await Promise.all(ids.map(script => this._browser._browserSession.send('script.removePreloadScript', { script })));
   }
 
   async doUpdateRequestInterception(): Promise<void> {
diff --git a/packages/playwright-core/src/server/bidi/bidiPage.ts b/packages/playwright-core/src/server/bidi/bidiPage.ts
index a7904baa1d..f8d379d179 100644
--- a/packages/playwright-core/src/server/bidi/bidiPage.ts
+++ b/packages/playwright-core/src/server/bidi/bidiPage.ts
@@ -50,6 +50,7 @@ export class BidiPage implements PageDelegate {
   readonly _browserContext: BidiBrowserContext;
   readonly _networkManager: BidiNetworkManager;
   private readonly _pdf: BidiPDF;
+  private _initScriptIds = new Map<InitScript, string>();
 
   constructor(browserContext: BidiBrowserContext, bidiSession: BidiSession, opener: BidiPage | null) {
     this._session = bidiSession;
@@ -341,11 +342,18 @@ export class BidiPage implements PageDelegate {
       // TODO: push to iframes?
       contexts: [this._session.sessionId],
     });
-    initScript.auxData = script;
+    this._initScriptIds.set(initScript, script);
   }
 
   async removeInitScripts(initScripts: InitScript[]): Promise<void> {
-    await Promise.all(initScripts.map(script => this._session.send('script.removePreloadScript', { script: script.auxData })));
+    const ids: string[] = [];
+    for (const script of initScripts) {
+      const id = this._initScriptIds.get(script);
+      if (id)
+        ids.push(id);
+      this._initScriptIds.delete(script);
+    }
+    await Promise.all(ids.map(script => this._session.send('script.removePreloadScript', { script })));
   }
 
   async closePage(runBeforeUnload: boolean): Promise<void> {
diff --git a/packages/playwright-core/src/server/chromium/crPage.ts b/packages/playwright-core/src/server/chromium/crPage.ts
index 05e0c1bb94..5800a23201 100644
--- a/packages/playwright-core/src/server/chromium/crPage.ts
+++ b/packages/playwright-core/src/server/chromium/crPage.ts
@@ -394,6 +394,7 @@ class FrameSession {
   private _screencastClients = new Set<any>();
   private _metricsOverride: Protocol.Emulation.setDeviceMetricsOverrideParameters | undefined;
   private _workerSessions = new Map<string, CRSession>();
+  private _initScriptIds = new Map<InitScript, string>();
 
   constructor(crPage: CRPage, client: CRSession, targetId: string, parentSession: FrameSession | null) {
     this._client = client;
@@ -1058,11 +1059,18 @@ class FrameSession {
   async _evaluateOnNewDocument(initScript: InitScript, world: types.World, runImmediately?: boolean): Promise<void> {
     const worldName = world === 'utility' ? this._crPage.utilityWorldName : undefined;
     const { identifier } = await this._client.send('Page.addScriptToEvaluateOnNewDocument', { source: initScript.source, worldName, runImmediately });
-    initScript.auxData = identifier;
+    this._initScriptIds.set(initScript, identifier);
   }
 
   async _removeEvaluatesOnNewDocument(initScripts: InitScript[]): Promise<void> {
-    await Promise.all(initScripts.map(script => this._client.send('Page.removeScriptToEvaluateOnNewDocument', { identifier: script.auxData }).catch(() => {}))); // target can be closed
+    const ids: string[] = [];
+    for (const script of initScripts) {
+      const id = this._initScriptIds.get(script);
+      if (id)
+        ids.push(id);
+      this._initScriptIds.delete(script);
+    }
+    await Promise.all(ids.map(identifier => this._client.send('Page.removeScriptToEvaluateOnNewDocument', { identifier }).catch(() => {}))); // target can be closed
   }
 
   async exposePlaywrightBinding() {
diff --git a/packages/playwright-core/src/server/page.ts b/packages/playwright-core/src/server/page.ts
index a6952796aa..9627308633 100644
--- a/packages/playwright-core/src/server/page.ts
+++ b/packages/playwright-core/src/server/page.ts
@@ -914,7 +914,6 @@ export class PageBinding {
 export class InitScript {
   readonly source: string;
   readonly name?: string;
-  auxData: any; // Can be arbitrarily used by a browser-specific implementation.
 
   constructor(source: string, name?: string) {
     this.source = `(() => {