diff --git a/testing/web-platform/tests/interfaces/fullscreen.idl b/testing/web-platform/tests/interfaces/fullscreen.idl
index 6f86d5c220fd..677b2e116f6d 100644
--- a/testing/web-platform/tests/interfaces/fullscreen.idl
+++ b/testing/web-platform/tests/interfaces/fullscreen.idl
@@ -21,8 +21,8 @@ partial interface Element {
 };
 
 partial interface Document {
-  [LenientSetter] readonly attribute boolean fullscreenEnabled;
-  [LenientSetter, Unscopable] readonly attribute boolean fullscreen; // historical
+  [LegacyLenientSetter] readonly attribute boolean fullscreenEnabled;
+  [LegacyLenientSetter, Unscopable] readonly attribute boolean fullscreen; // historical
 
   Promise<void> exitFullscreen();
 
@@ -31,5 +31,5 @@ partial interface Document {
 };
 
 partial interface mixin DocumentOrShadowRoot {
-  [LenientSetter] readonly attribute Element? fullscreenElement;
+  [LegacyLenientSetter] readonly attribute Element? fullscreenElement;
 };
diff --git a/testing/web-platform/tests/resources/idlharness.js b/testing/web-platform/tests/resources/idlharness.js
index a5e2ca0b25ab..039a6bba96cd 100644
--- a/testing/web-platform/tests/resources/idlharness.js
+++ b/testing/web-platform/tests/resources/idlharness.js
@@ -3088,6 +3088,7 @@ IdlInterface.prototype.do_interface_attribute_asserts = function(obj, member, a_
     // TypeError in most cases).
     if (member.readonly
     && !member.has_extended_attribute("LenientSetter")
+    && !member.has_extended_attribute("LegacyLenientSetter")
     && !member.has_extended_attribute("PutForwards")
     && !member.has_extended_attribute("Replaceable"))
     {