diff --git a/dom/tests/mochitest/general/test_interfaces.html b/dom/tests/mochitest/general/test_interfaces.html
index 13a76ce992..77993a1aff 100644
--- a/dom/tests/mochitest/general/test_interfaces.html
+++ b/dom/tests/mochitest/general/test_interfaces.html
@@ -715,8 +715,6 @@ var interfaceNamesInGlobalScope =
     "NodeList",
 // IMPORTANT: Do not change this list without review from a DOM peer!
     "Notification",
-// IMPORTANT: Do not change this list without review from a DOM peer!
-    "NotifyPaintEvent",
 // IMPORTANT: Do not change this list without review from a DOM peer!
     {name: "OffscreenCanvas", disabled: true},
 // IMPORTANT: Do not change this list without review from a DOM peer!
diff --git a/dom/webidl/NotifyPaintEvent.webidl b/dom/webidl/NotifyPaintEvent.webidl
index 799abbb299..b4be1c3a79 100644
--- a/dom/webidl/NotifyPaintEvent.webidl
+++ b/dom/webidl/NotifyPaintEvent.webidl
@@ -6,13 +6,18 @@
  * For more information about this interface see nsIDOMNotifyPaintEvent.idl
  */
 
+[ChromeOnly]
 interface NotifyPaintEvent : Event
 {
+  [ChromeOnly]
   readonly attribute DOMRectList clientRects;
 
+  [ChromeOnly]
   readonly attribute DOMRect boundingClientRect;
 
+  [ChromeOnly]
   readonly attribute PaintRequestList paintRequests;
 
+  [ChromeOnly]
   readonly attribute unsigned long long transactionId;
 };
diff --git a/layout/base/tests/test_after_paint_pref.html b/layout/base/tests/test_after_paint_pref.html
index 33a8c71625..c1a8e6a294 100644
--- a/layout/base/tests/test_after_paint_pref.html
+++ b/layout/base/tests/test_after_paint_pref.html
@@ -24,14 +24,19 @@ window.addEventListener("load", step0, false);
 is(SpecialPowers.getBoolPref("dom.send_after_paint_to_content"), true, "pref defaults to true in mochitest harness");
 
 function print_rect(rect) {
+  if (!rect) {
+    rect = { top: 0, left: 0, width: 0, right: 0 };
+  }
   return "(top=" + rect.top + ",left=" + rect.left + ",width=" + rect.width + ",height=" + rect.height + ")";
 }
 
 function print_event(event) {
   var res = "boundingClientRect=" + print_rect(event.boundingClientRect);
   var rects = event.clientRects;
-  for (var i = 0; i < rects.length; ++i) {
-    res += " clientRects[" + i + "]=" + print_rect(rects[i]);
+  if (rects) {
+    for (var i = 0; i < rects.length; ++i) {
+      res += " clientRects[" + i + "]=" + print_rect(rects[i]);
+    }
   }
   return res;
 }
diff --git a/testing/mochitest/tests/SimpleTest/paint_listener.js b/testing/mochitest/tests/SimpleTest/paint_listener.js
index 304a0fd629..4054ce0d0e 100644
--- a/testing/mochitest/tests/SimpleTest/paint_listener.js
+++ b/testing/mochitest/tests/SimpleTest/paint_listener.js
@@ -10,11 +10,15 @@
   function paintListener(event) {
     if (event.target != window)
       return;
-    var eventRect =
-      [ event.boundingClientRect.left,
-        event.boundingClientRect.top,
-        event.boundingClientRect.right,
-        event.boundingClientRect.bottom ];
+    var clientRect = event.boundingClientRect;
+    var eventRect;
+    if (clientRect) {
+      eventRect =
+        [ clientRect.left, clientRect.top,
+          clientRect.right, clientRect.bottom ];
+    } else {
+      eventRect = [ 0, 0, 0, 0 ];
+    }
     if (debug) {
       dump("got MozAfterPaint: " + eventRect.join(",") + "\n");
     }