diff --git a/dom/security/test/csp/browser_pdfjs_not_subject_to_csp.js b/dom/security/test/csp/browser_pdfjs_not_subject_to_csp.js
index a765f5bcff2b..2391e955bafb 100644
--- a/dom/security/test/csp/browser_pdfjs_not_subject_to_csp.js
+++ b/dom/security/test/csp/browser_pdfjs_not_subject_to_csp.js
@@ -6,9 +6,6 @@ const TEST_PATH = getRootDirectory(gTestPath).replace(
 );
 
 add_task(async function () {
-  await SpecialPowers.pushPrefEnv({
-    set: [["pdfjs.eventBusDispatchToDOM", true]],
-  });
   await BrowserTestUtils.withNewTab(
     TEST_PATH + "file_pdfjs_not_subject_to_csp.html",
     async function (browser) {
diff --git a/testing/perfdocs/generated/talos.rst b/testing/perfdocs/generated/talos.rst
index 4a82a42f490f..f1c289962da4 100644
--- a/testing/perfdocs/generated/talos.rst
+++ b/testing/perfdocs/generated/talos.rst
@@ -3446,7 +3446,6 @@ For the sample commands found below, note that the capitalization used is import
    * reporting: time from *performance.timing.navigationStart* to *pagerendered* event in ms (lower is better)
    * data: load a PDF 20 times
    * pdfpaint: True
-   * preferences: {'pdfjs.eventBusDispatchToDOM': True}
    * timeout: 600
    * tpmanifest: ${talos}/tests/pdfpaint/pdfpaint.manifest
    * tppagecycles: 20
diff --git a/testing/talos/talos/test.py b/testing/talos/talos/test.py
index 95c14bb46d24..06598847634e 100644
--- a/testing/talos/talos/test.py
+++ b/testing/talos/talos/test.py
@@ -422,7 +422,6 @@ class pdfpaint(PageloaderTest):
     timeout = 600
     pdfpaint = True
     unit = "ms"
-    preferences = {"pdfjs.eventBusDispatchToDOM": True}
 
 
 @register_test()
diff --git a/toolkit/components/printing/tests/head.js b/toolkit/components/printing/tests/head.js
index 72033c93cb8c..f06acc6212ba 100644
--- a/toolkit/components/printing/tests/head.js
+++ b/toolkit/components/printing/tests/head.js
@@ -19,12 +19,6 @@ class PrintHelper {
     info("withTestPage: " + pageUrl);
     let isPdf = pageUrl.endsWith(".pdf");
 
-    if (isPdf) {
-      await SpecialPowers.pushPrefEnv({
-        set: [["pdfjs.eventBusDispatchToDOM", true]],
-      });
-    }
-
     let taskReturn = await BrowserTestUtils.withNewTab(
       isPdf ? "about:blank" : pageUrl,
       async function (browser) {
diff --git a/uriloader/exthandler/tests/mochitest/browser_download_open_with_internal_handler.js b/uriloader/exthandler/tests/mochitest/browser_download_open_with_internal_handler.js
index e39d9ff04ff4..c6fa37e9e35d 100644
--- a/uriloader/exthandler/tests/mochitest/browser_download_open_with_internal_handler.js
+++ b/uriloader/exthandler/tests/mochitest/browser_download_open_with_internal_handler.js
@@ -35,9 +35,6 @@ function waitForAcceptButtonToGetEnabled(doc) {
 }
 
 async function waitForPdfJS(browser, url) {
-  await SpecialPowers.pushPrefEnv({
-    set: [["pdfjs.eventBusDispatchToDOM", true]],
-  });
   // Runs tests after all "load" event handlers have fired off
   let loadPromise = BrowserTestUtils.waitForContentEvent(
     browser,