diff --git a/tests/wpt/mozilla/meta/mozilla/interfaces.html.ini b/tests/wpt/mozilla/meta/mozilla/interfaces.html.ini
deleted file mode 100644
index 378eade335e..00000000000
--- a/tests/wpt/mozilla/meta/mozilla/interfaces.html.ini
+++ /dev/null
@@ -1,4 +0,0 @@
-[interfaces.html]
-  [Interfaces exposed on the window]
-    expected: FAIL
-
diff --git a/tests/wpt/mozilla/meta/mozilla/interfaces.worker.js.ini b/tests/wpt/mozilla/meta/mozilla/interfaces.worker.js.ini
deleted file mode 100644
index 701d363381a..00000000000
--- a/tests/wpt/mozilla/meta/mozilla/interfaces.worker.js.ini
+++ /dev/null
@@ -1,4 +0,0 @@
-[interfaces.worker.html]
-  [interfaces]
-    expected: FAIL
-
diff --git a/tests/wpt/mozilla/tests/mozilla/interfaces.js b/tests/wpt/mozilla/tests/mozilla/interfaces.js
index 786f6e12515..c46c336f8a8 100644
--- a/tests/wpt/mozilla/tests/mozilla/interfaces.js
+++ b/tests/wpt/mozilla/tests/mozilla/interfaces.js
@@ -55,7 +55,7 @@ function test_interfaces(interfaceNamesInGlobalScope) {
     var sources = [
       ecmaGlobals,
       interfaceNamesInGlobalScope,
-      ["AssertionError", "EventWatcher"],
+      ["AssertionError", "EventWatcher", "PreconditionFailedError"],
     ];
 
     var interfaceMap = {};