diff --git a/accessible/generic/DocAccessible.cpp b/accessible/generic/DocAccessible.cpp
index 425c6a59deebda17773e15c291c9e0a481df0110..f231ffc59bc3a58f611943b42dcbec47d5f07242 100644
--- a/accessible/generic/DocAccessible.cpp
+++ b/accessible/generic/DocAccessible.cpp
@@ -399,6 +399,10 @@ void DocAccessible::Init() {
     // harm even if it isn't necessary. We set mLoadEventType here and it will
     // be fired in ProcessLoad as usual.
     mLoadEventType = nsIAccessibleEvent::EVENT_DOCUMENT_LOAD_COMPLETE;
+  } else if (mDocumentNode->IsInitialDocument()) {
+    // The initial about:blank document will never finish loading, so we can
+    // immediately mark it loaded to avoid waiting for its load.
+    mLoadState |= eDOMLoaded;
   }
 
   AddEventListeners();
diff --git a/browser/base/content/test/performance/browser.ini b/browser/base/content/test/performance/browser.ini
index 7c03f5f69c720820c2a487e138b7f11bf41b0fab..5715f0e23ccf8c740d4a82985b993036ef267232 100644
--- a/browser/base/content/test/performance/browser.ini
+++ b/browser/base/content/test/performance/browser.ini
@@ -74,6 +74,7 @@ skip-if = os == 'win' #Bug 1455054
 skip-if = (os == 'win' && bits == 32) || (os == 'mac') # Disabled on Win32 because of intermittent OOM failures (bug 1448241), macosx1014 due to 1565619
 [browser_urlbar_search.js]
 skip-if = (debug || ccov) && (os == 'linux' || os == 'win') || (os == 'win' && bits == 32) # Disabled on Linux and Windows debug and ccov due to intermittent timeouts. Bug 1414126, bug 1426611. Disabled on Win32 because of intermittent OOM failures (bug 1448241)
+[browser_vsync_accessibility.js]
 [browser_window_resize.js]
 [browser_windowclose.js]
 [browser_windowopen.js]
diff --git a/browser/base/content/test/performance/browser_vsync_accessibility.js b/browser/base/content/test/performance/browser_vsync_accessibility.js
new file mode 100644
index 0000000000000000000000000000000000000000..9718f11886d7b7eb37828d429919e5433c78f091
--- /dev/null
+++ b/browser/base/content/test/performance/browser_vsync_accessibility.js
@@ -0,0 +1,20 @@
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+"use strict";
+
+add_task(async function() {
+  await TestUtils.waitForCondition(
+    () => !ChromeUtils.vsyncEnabled(),
+    "wait for vsync to be disabled at the start of the test"
+  );
+  Assert.ok(!ChromeUtils.vsyncEnabled(), "vsync should be disabled");
+  Cc["@mozilla.org/accessibilityService;1"].getService(
+    Ci.nsIAccessibilityService
+  );
+  await TestUtils.waitForCondition(
+    () => !ChromeUtils.vsyncEnabled(),
+    "wait for vsync to be disabled after initializing the accessibility service"
+  );
+  Assert.ok(!ChromeUtils.vsyncEnabled(), "vsync should still be disabled");
+});