diff --git a/components/script/dom/webidls/Window.webidl b/components/script/dom/webidls/Window.webidl
index 1679fa42887..81ffee9283e 100644
--- a/components/script/dom/webidls/Window.webidl
+++ b/components/script/dom/webidls/Window.webidl
@@ -72,9 +72,6 @@
 Window implements GlobalEventHandlers;
 Window implements WindowEventHandlers;
 
-[NoInterfaceObject]
-interface WindowProxy {};
-
 // https://html.spec.whatwg.org/multipage/#Window-partial
 partial interface Window {
   void captureEvents();
diff --git a/components/script/dom/webidls/WindowProxy.webidl b/components/script/dom/webidls/WindowProxy.webidl
new file mode 100644
index 00000000000..897f86c295b
--- /dev/null
+++ b/components/script/dom/webidls/WindowProxy.webidl
@@ -0,0 +1,7 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
+
+// https://html.spec.whatwg.org/multipage/#the-windowproxy-exotic-object
+[NoInterfaceObject]
+interface WindowProxy {};