diff --git a/resources/idlharness-shadowrealm.js b/resources/idlharness-shadowrealm.js
index 9484ca6f512ad0..ff5db106d8ca21 100644
--- a/resources/idlharness-shadowrealm.js
+++ b/resources/idlharness-shadowrealm.js
@@ -23,9 +23,6 @@ function fetch_text(url) {
 function idl_test_shadowrealm(srcs, deps) {
     promise_setup(async t => {
         const realm = new ShadowRealm();
-        // https://github.com/web-platform-tests/wpt/issues/31996
-        realm.evaluate("globalThis.self = globalThis; undefined;");
-
         realm.evaluate(`
             globalThis.self.GLOBAL = {
                 isWindow: function() { return false; },
diff --git a/tools/serve/serve.py b/tools/serve/serve.py
index 98024393c94da3..fbafd08438d402 100644
--- a/tools/serve/serve.py
+++ b/tools/serve/serve.py
@@ -438,7 +438,6 @@ class ShadowRealmInWindowHandler(HtmlWrapperHandler):
 <script>
 (async function() {
   const r = new ShadowRealm();
-  r.evaluate("globalThis.self = globalThis; undefined;");
   r.evaluate(`func => {
     globalThis.fetch_json = (resource) => {
       const thenMethod = func(resource);