diff --git a/toolkit/modules/RemotePageManager.jsm b/toolkit/modules/RemotePageManager.jsm
index c601a89cea90..b571b620b4c5 100644
--- a/toolkit/modules/RemotePageManager.jsm
+++ b/toolkit/modules/RemotePageManager.jsm
@@ -389,7 +389,7 @@ function ChildMessagePort(contentFrame, window) {
   // Tell the main process to set up its side of the message pipe.
   this.messageManager.sendAsyncMessage("RemotePage:InitPort", {
     portID: portID,
-    url: window.location.toString().replace(/\#.*$/, "")
+    url: window.document.documentURI.replace(/[\#|\?].*$/, ""),
   });
 }
 
@@ -491,7 +491,7 @@ var registeredURLs = new Set();
 
 var observer = (window) => {
   // Strip the hash from the URL, because it's not part of the origin.
-  let url = window.location.toString().replace(/\#.*$/, "");
+  let url = window.document.documentURI.replace(/[\#|\?].*$/, "");
   if (!registeredURLs.has(url))
     return;