diff --git a/extensions/chromium/preferences_schema.json b/extensions/chromium/preferences_schema.json
index 5b428bc6e..add31dae3 100644
--- a/extensions/chromium/preferences_schema.json
+++ b/extensions/chromium/preferences_schema.json
@@ -58,10 +58,6 @@
       "type": "boolean",
       "default": false
     },
-    "eventBusDispatchToDOM": {
-      "type": "boolean",
-      "default": false
-    },
     "pdfBugEnabled": {
       "title": "Enable debugging tools",
       "description": "Whether to enable debugging tools.",
diff --git a/test/unit/ui_utils_spec.js b/test/unit/ui_utils_spec.js
index b60c783d3..132aa3b72 100644
--- a/test/unit/ui_utils_spec.js
+++ b/test/unit/ui_utils_spec.js
@@ -312,7 +312,7 @@ describe("ui_utils", function() {
       expect(count).toEqual(2);
     });
 
-    it("should not, by default, re-dispatch to DOM", function(done) {
+    it("should not re-dispatch to DOM", function(done) {
       if (isNodeJS) {
         pending("Document in not supported in Node.js.");
       }
@@ -329,54 +329,6 @@ describe("ui_utils", function() {
 
       eventBus.dispatch("test");
 
-      Promise.resolve().then(() => {
-        expect(count).toEqual(1);
-
-        document.removeEventListener("test", domEventListener);
-        done();
-      });
-    });
-    it("should re-dispatch to DOM", function(done) {
-      if (isNodeJS) {
-        pending("Document in not supported in Node.js.");
-      }
-      const eventBus = new EventBus({ dispatchToDOM: true });
-      let count = 0;
-      eventBus.on("test", function(evt) {
-        expect(evt).toEqual(undefined);
-        count++;
-      });
-      function domEventListener(evt) {
-        expect(evt.detail).toEqual({});
-        count++;
-      }
-      document.addEventListener("test", domEventListener);
-
-      eventBus.dispatch("test");
-
-      Promise.resolve().then(() => {
-        expect(count).toEqual(2);
-
-        document.removeEventListener("test", domEventListener);
-        done();
-      });
-    });
-    it("should re-dispatch to DOM, with arguments (without internal listeners)", function(done) {
-      if (isNodeJS) {
-        pending("Document in not supported in Node.js.");
-      }
-      const eventBus = new EventBus({ dispatchToDOM: true });
-      let count = 0;
-      function domEventListener(evt) {
-        expect(evt.detail).toEqual({ abc: 123 });
-        count++;
-      }
-      document.addEventListener("test", domEventListener);
-
-      eventBus.dispatch("test", {
-        abc: 123,
-      });
-
       Promise.resolve().then(() => {
         expect(count).toEqual(1);
 
diff --git a/web/app.js b/web/app.js
index b1ebe23e1..155462fa3 100644
--- a/web/app.js
+++ b/web/app.js
@@ -125,6 +125,10 @@ class DefaultExternalServices {
       metaKey: true,
     });
   }
+
+  static get isInAutomation() {
+    return shadow(this, "isInAutomation", false);
+  }
 }
 
 const PDFViewerApplication = {
@@ -339,13 +343,13 @@ const PDFViewerApplication = {
   async _initializeViewerComponents() {
     const appConfig = this.appConfig;
 
-    this.overlayManager = new OverlayManager();
-
     const eventBus =
       appConfig.eventBus ||
-      new EventBus({ dispatchToDOM: AppOptions.get("eventBusDispatchToDOM") });
+      new EventBus({ isInAutomation: this.externalServices.isInAutomation });
     this.eventBus = eventBus;
 
+    this.overlayManager = new OverlayManager();
+
     const pdfRenderingQueue = new PDFRenderingQueue();
     pdfRenderingQueue.onIdle = this.cleanup.bind(this);
     this.pdfRenderingQueue = pdfRenderingQueue;
diff --git a/web/app_options.js b/web/app_options.js
index 3e4736299..3fa1187a1 100644
--- a/web/app_options.js
+++ b/web/app_options.js
@@ -66,11 +66,6 @@ const defaultOptions = {
     value: false,
     kind: OptionKind.VIEWER + OptionKind.PREFERENCE,
   },
-  eventBusDispatchToDOM: {
-    /** @type {boolean} */
-    value: false,
-    kind: OptionKind.VIEWER + OptionKind.PREFERENCE,
-  },
   externalLinkRel: {
     /** @type {string} */
     value: "noopener noreferrer nofollow",
diff --git a/web/firefoxcom.js b/web/firefoxcom.js
index 75e55a2db..d0167f888 100644
--- a/web/firefoxcom.js
+++ b/web/firefoxcom.js
@@ -345,6 +345,13 @@ class FirefoxExternalServices extends DefaultExternalServices {
     );
     return shadow(this, "supportedMouseWheelZoomModifierKeys", support);
   }
+
+  static get isInAutomation() {
+    // Returns the value of `Cu.isInAutomation`, which is only `true` when e.g.
+    // various test-suites are running in mozilla-central.
+    const isInAutomation = FirefoxCom.requestSync("isInAutomation");
+    return shadow(this, "isInAutomation", isInAutomation);
+  }
 }
 PDFViewerApplication.externalServices = FirefoxExternalServices;
 
diff --git a/web/ui_utils.js b/web/ui_utils.js
index 1841860dd..5ea91834a 100644
--- a/web/ui_utils.js
+++ b/web/ui_utils.js
@@ -760,6 +760,9 @@ const animationStarted = new Promise(function(resolve) {
  * NOTE: Only used to support various PDF viewer tests in `mozilla-central`.
  */
 function dispatchDOMEvent(eventName, args = null) {
+  if (typeof PDFJSDev !== "undefined" && !PDFJSDev.test("MOZCENTRAL")) {
+    throw new Error("Not implemented: dispatchDOMEvent");
+  }
   const details = Object.create(null);
   if (args && args.length > 0) {
     const obj = args[0];
@@ -784,19 +787,11 @@ function dispatchDOMEvent(eventName, args = null) {
  * and `off` methods. To raise an event, the `dispatch` method shall be used.
  */
 class EventBus {
-  constructor({ dispatchToDOM = false } = {}) {
+  constructor(options) {
     this._listeners = Object.create(null);
-    this._dispatchToDOM = dispatchToDOM === true;
 
-    if (
-      typeof PDFJSDev !== "undefined" &&
-      !PDFJSDev.test("MOZCENTRAL || TESTING") &&
-      dispatchToDOM
-    ) {
-      console.error(
-        "The `eventBusDispatchToDOM` option/preference is deprecated, " +
-          "add event listeners to the EventBus instance rather than the DOM."
-      );
+    if (typeof PDFJSDev === "undefined" || PDFJSDev.test("MOZCENTRAL")) {
+      this._isInAutomation = (options && options.isInAutomation) === true;
     }
   }
 
@@ -819,7 +814,10 @@ class EventBus {
   dispatch(eventName) {
     const eventListeners = this._listeners[eventName];
     if (!eventListeners || eventListeners.length === 0) {
-      if (this._dispatchToDOM) {
+      if (
+        (typeof PDFJSDev === "undefined" || PDFJSDev.test("MOZCENTRAL")) &&
+        this._isInAutomation
+      ) {
         const args = Array.prototype.slice.call(arguments, 1);
         dispatchDOMEvent(eventName, args);
       }
@@ -848,7 +846,10 @@ class EventBus {
       });
       externalListeners = null;
     }
-    if (this._dispatchToDOM) {
+    if (
+      (typeof PDFJSDev === "undefined" || PDFJSDev.test("MOZCENTRAL")) &&
+      this._isInAutomation
+    ) {
       dispatchDOMEvent(eventName, args);
     }
   }