--- a/toolkit/content/browser-child.js
+++ b/toolkit/content/browser-child.js
@@ -42,16 +42,25 @@ let WebProgressListener = {
                      .createInstance(Ci.nsIWebProgress);
     this._filter.addProgressListener(this, Ci.nsIWebProgress.NOTIFY_ALL);
 
     let webProgress = docShell.QueryInterface(Ci.nsIInterfaceRequestor)
                               .getInterface(Ci.nsIWebProgress);
     webProgress.addProgressListener(this._filter, Ci.nsIWebProgress.NOTIFY_ALL);
   },
 
+  uninit() {
+    let webProgress = docShell.QueryInterface(Ci.nsIInterfaceRequestor)
+                              .getInterface(Ci.nsIWebProgress);
+    webProgress.removeProgressListener(this._filter);
+
+    this._filter.removeProgressListener(this);
+    this._filter = null;
+  },
+
   _requestSpec: function (aRequest, aPropertyName) {
     if (!aRequest || !(aRequest instanceof Ci.nsIChannel))
       return null;
     return aRequest.QueryInterface(Ci.nsIChannel)[aPropertyName].spec;
   },
 
   _setupJSON: function setupJSON(aWebProgress, aRequest) {
     if (aWebProgress) {
@@ -149,16 +158,19 @@ let WebProgressListener = {
         return this;
     }
 
     throw Components.results.NS_ERROR_NO_INTERFACE;
   }
 };
 
 WebProgressListener.init();
+addEventListener("unload", () => {
+  WebProgressListener.uninit();
+});
 
 let WebNavigation =  {
   init: function() {
     addMessageListener("WebNavigation:GoBack", this);
     addMessageListener("WebNavigation:GoForward", this);
     addMessageListener("WebNavigation:GotoIndex", this);
     addMessageListener("WebNavigation:LoadURI", this);
     addMessageListener("WebNavigation:Reload", this);