diff --git a/src/display/api.js b/src/display/api.js
index 08b34aa46..b21e02aff 100644
--- a/src/display/api.js
+++ b/src/display/api.js
@@ -2061,7 +2061,7 @@ if (typeof PDFJSDev === "undefined" || PDFJSDev.test("GENERIC")) {
  * @param {PDFWorkerParameters} params - The worker initialization parameters.
  */
 class PDFWorker {
-  static #workerPorts = new WeakMap();
+  static #workerPorts;
 
   constructor({
     name = null,
@@ -2077,11 +2077,14 @@ class PDFWorker {
     this._webWorker = null;
     this._messageHandler = null;
 
-    if (port) {
-      if (PDFWorker.#workerPorts.has(port)) {
+    if (
+      (typeof PDFJSDev === "undefined" || !PDFJSDev.test("MOZCENTRAL")) &&
+      port
+    ) {
+      if (PDFWorker.#workerPorts?.has(port)) {
         throw new Error("Cannot use more than one PDFWorker per port.");
       }
-      PDFWorker.#workerPorts.set(port, this);
+      (PDFWorker.#workerPorts ||= new WeakMap()).set(port, this);
       this._initializeFromPort(port);
       return;
     }
@@ -2113,6 +2116,9 @@ class PDFWorker {
   }
 
   _initializeFromPort(port) {
+    if (typeof PDFJSDev !== "undefined" && PDFJSDev.test("MOZCENTRAL")) {
+      throw new Error("Not implemented: _initializeFromPort");
+    }
     this._port = port;
     this._messageHandler = new MessageHandler("main", "worker", port);
     this._messageHandler.on("ready", function () {
@@ -2284,7 +2290,7 @@ class PDFWorker {
       this._webWorker.terminate();
       this._webWorker = null;
     }
-    PDFWorker.#workerPorts.delete(this._port);
+    PDFWorker.#workerPorts?.delete(this._port);
     this._port = null;
     if (this._messageHandler) {
       this._messageHandler.destroy();
@@ -2302,7 +2308,7 @@ class PDFWorker {
     if (!params?.port) {
       throw new Error("PDFWorker.fromPort - invalid method signature.");
     }
-    const cachedPort = this.#workerPorts.get(params.port);
+    const cachedPort = this.#workerPorts?.get(params.port);
     if (cachedPort) {
       if (cachedPort._pendingDestroy) {
         throw new Error(