diff --git a/addon/webextension/assertIsTrusted.js b/addon/webextension/assertIsTrusted.js
index ea606097c6..d80e83ac80 100644
--- a/addon/webextension/assertIsTrusted.js
+++ b/addon/webextension/assertIsTrusted.js
@@ -2,7 +2,7 @@
       https://developer.mozilla.org/en-US/docs/Web/API/Event/isTrusted
     Should be applied *inside* catcher.watchFunction
 */
-function assertIsTrusted(handlerFunction) {
+this.assertIsTrusted = function assertIsTrusted(handlerFunction) {
   return function (event) {
     if (! event) {
       let exc = new Error("assertIsTrusted did not get an event");
@@ -17,3 +17,4 @@ function assertIsTrusted(handlerFunction) {
     return handlerFunction.call(this, event);
   };
 }
+null;
diff --git a/addon/webextension/background/analytics.js b/addon/webextension/background/analytics.js
index 81d805263c..ed41bca2bb 100644
--- a/addon/webextension/background/analytics.js
+++ b/addon/webextension/background/analytics.js
@@ -2,7 +2,7 @@
 
 "use strict";
 
-window.analytics = (function () {
+this.analytics = (function () {
   let exports = {};
 
   let telemetryPrefKnown = false;
diff --git a/addon/webextension/background/auth.js b/addon/webextension/background/auth.js
index a14f2cdce3..05ccfb588d 100644
--- a/addon/webextension/background/auth.js
+++ b/addon/webextension/background/auth.js
@@ -3,7 +3,7 @@
 
 "use strict";
 
-window.auth = (function () {
+this.auth = (function () {
   let exports = {};
 
   let registrationInfo;
diff --git a/addon/webextension/background/communication.js b/addon/webextension/background/communication.js
index 2995d7a001..d837df8a81 100644
--- a/addon/webextension/background/communication.js
+++ b/addon/webextension/background/communication.js
@@ -2,7 +2,7 @@
 
 "use strict";
 
-window.communication = (function () {
+this.communication = (function () {
   let exports = {};
 
   let registeredFunctions = {};
diff --git a/addon/webextension/background/deviceInfo.js b/addon/webextension/background/deviceInfo.js
index 0137f5cb6e..9ab5bb00c2 100644
--- a/addon/webextension/background/deviceInfo.js
+++ b/addon/webextension/background/deviceInfo.js
@@ -2,7 +2,7 @@
 
 "use strict";
 
-window.deviceInfo = (function () {
+this.deviceInfo = (function () {
   let manifest = browser.runtime.getManifest();
 
   let platformInfo = {};
diff --git a/addon/webextension/background/main.js b/addon/webextension/background/main.js
index 560c9f7947..b7b0f3fec1 100644
--- a/addon/webextension/background/main.js
+++ b/addon/webextension/background/main.js
@@ -3,7 +3,7 @@
 
 "use strict";
 
-window.main = (function () {
+this.main = (function () {
   let exports = {};
 
   const pasteSymbol = (window.navigator.platform.match(/Mac/i)) ? "\u2318" : "Ctrl";
diff --git a/addon/webextension/background/selectorLoader.js b/addon/webextension/background/selectorLoader.js
index 6ced014b94..37e6f2cd23 100644
--- a/addon/webextension/background/selectorLoader.js
+++ b/addon/webextension/background/selectorLoader.js
@@ -2,7 +2,7 @@
 
 "use strict";
 
-window.selectorLoader = (function () {
+this.selectorLoader = (function () {
   const exports = {};
 
   // These modules are loaded in order, first standardScripts, then optionally onboardingScripts, and then selectorScripts
@@ -37,10 +37,10 @@ window.selectorLoader = (function () {
 
   exports.unloadIfLoaded = function (tabId) {
     return browser.tabs.executeScript(tabId, {
-      code: "window.selectorLoader && window.selectorLoader.unloadModules()",
+      code: "this.selectorLoader && this.selectorLoader.unloadModules()",
       runAt: "document_start"
     }).then(result => {
-      return result && result.toString() === "true";
+      return result && result[0];
     });
   };
 
@@ -84,7 +84,7 @@ window.selectorLoader = (function () {
       filename.replace(/^.*\//, "").replace(/\.js$/, ""));
     moduleNames.reverse();
     for (let moduleName of moduleNames) {
-      let moduleObj = window[moduleName];
+      let moduleObj = global[moduleName];
       if (moduleObj && moduleObj.unload) {
         try {
           watchFunction(moduleObj.unload)();
@@ -92,7 +92,7 @@ window.selectorLoader = (function () {
           // ignore (watchFunction handles it)
         }
       }
-      delete window[moduleName];
+      delete global[moduleName];
     }
     return true;
   };
diff --git a/addon/webextension/background/senderror.js b/addon/webextension/background/senderror.js
index c9a8eda634..d096423dee 100644
--- a/addon/webextension/background/senderror.js
+++ b/addon/webextension/background/senderror.js
@@ -2,7 +2,7 @@
 
 "use strict";
 
-window.senderror = (function () {
+this.senderror = (function () {
   let exports = {};
 
   // Do not show an error more than every ERROR_TIME_LIMIT milliseconds:
diff --git a/addon/webextension/background/takeshot.js b/addon/webextension/background/takeshot.js
index 38c99f2325..3d7c090282 100644
--- a/addon/webextension/background/takeshot.js
+++ b/addon/webextension/background/takeshot.js
@@ -2,7 +2,7 @@
 
 "use strict";
 
-window.takeshot = (function () {
+this.takeshot = (function () {
   let exports = {};
   const Shot = shot.AbstractShot;
   const { sendEvent } = analytics;
diff --git a/addon/webextension/catcher.js b/addon/webextension/catcher.js
index d1a7248085..7810da313a 100644
--- a/addon/webextension/catcher.js
+++ b/addon/webextension/catcher.js
@@ -1,6 +1,8 @@
 "use strict";
 
-window.catcher = (function () {
+var global = this;
+
+this.catcher = (function () {
   let exports = {};
 
   let handler;
diff --git a/addon/webextension/clipboard.js b/addon/webextension/clipboard.js
index c9dd84bd12..5eb799577f 100644
--- a/addon/webextension/clipboard.js
+++ b/addon/webextension/clipboard.js
@@ -2,7 +2,7 @@
 
 "use strict";
 
-window.clipboard = (function () {
+this.clipboard = (function () {
   let exports = {};
 
   exports.copy = function (text) {
diff --git a/addon/webextension/domainFromUrl.js b/addon/webextension/domainFromUrl.js
index 6f8f4e6d05..4b68d6caf5 100644
--- a/addon/webextension/domainFromUrl.js
+++ b/addon/webextension/domainFromUrl.js
@@ -4,7 +4,7 @@
 
 "use strict";
 
-window.domainFromUrl = (function () {
+this.domainFromUrl = (function () {
 
   return function urlDomainForId(location) { // eslint-disable-line no-unused-vars
     let domain = location.hostname;
diff --git a/addon/webextension/makeUuid.js b/addon/webextension/makeUuid.js
index 12e6d98a23..17d43625d4 100644
--- a/addon/webextension/makeUuid.js
+++ b/addon/webextension/makeUuid.js
@@ -1,6 +1,6 @@
 "use strict";
 
-window.makeUuid = (function () {
+this.makeUuid = (function () {
 
   // generates a v4 UUID
   return function makeUuid() { // eslint-disable-line no-unused-vars
diff --git a/addon/webextension/onboarding/slides.js b/addon/webextension/onboarding/slides.js
index 45a5ca92a5..a191f59c46 100644
--- a/addon/webextension/onboarding/slides.js
+++ b/addon/webextension/onboarding/slides.js
@@ -2,7 +2,7 @@
 
 "use strict";
 
-window.slides = (function () {
+this.slides = (function () {
   let exports = {};
 
   const { watchFunction } = catcher;
diff --git a/addon/webextension/randomString.js b/addon/webextension/randomString.js
index 072c2bdcef..3721927bad 100644
--- a/addon/webextension/randomString.js
+++ b/addon/webextension/randomString.js
@@ -2,7 +2,7 @@
 
 "use strict";
 
-function randomString(length, chars) {
+this.randomString = function randomString(length, chars) {
   let randomStringChars = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789";
   chars = chars || randomStringChars;
   let result = "";
diff --git a/addon/webextension/selector/callBackground.js b/addon/webextension/selector/callBackground.js
index b91996c58b..4f653fffc1 100644
--- a/addon/webextension/selector/callBackground.js
+++ b/addon/webextension/selector/callBackground.js
@@ -2,7 +2,7 @@
 
 "use strict";
 
-function callBackground (funcName, ...args) {
+this.callBackground = function callBackground (funcName, ...args) {
   return browser.runtime.sendMessage({funcName, args}).then((result) => {
     if (result.type === "success") {
       return result.value;
diff --git a/addon/webextension/selector/documentMetadata.js b/addon/webextension/selector/documentMetadata.js
index 23609e70f1..fc93b013c6 100644
--- a/addon/webextension/selector/documentMetadata.js
+++ b/addon/webextension/selector/documentMetadata.js
@@ -1,6 +1,6 @@
 "use strict";
 
-window.documentMetadata = (function () {
+this.documentMetadata = (function () {
 
   function findSiteName() {
     let el = document.querySelector("meta[property='og:site_name']");
diff --git a/addon/webextension/selector/shooter.js b/addon/webextension/selector/shooter.js
index 511073d74a..1840a5cab5 100644
--- a/addon/webextension/selector/shooter.js
+++ b/addon/webextension/selector/shooter.js
@@ -4,7 +4,7 @@
 
 "use strict";
 
-window.shooter = (function () { // eslint-disable-line no-unused-vars
+this.shooter = (function () { // eslint-disable-line no-unused-vars
   let exports = {};
   const { AbstractShot } = window.shot;
 
diff --git a/addon/webextension/selector/ui.js b/addon/webextension/selector/ui.js
index c3d9c6a038..4bc54b6bc0 100644
--- a/addon/webextension/selector/ui.js
+++ b/addon/webextension/selector/ui.js
@@ -3,7 +3,7 @@
 
 "use strict";
 
-window.ui = (function () { // eslint-disable-line no-unused-vars
+this.ui = (function () { // eslint-disable-line no-unused-vars
   let exports = {};
   const SAVE_BUTTON_HEIGHT = 50;
 
diff --git a/addon/webextension/selector/uicontrol.js b/addon/webextension/selector/uicontrol.js
index 88aba680c6..462d803596 100644
--- a/addon/webextension/selector/uicontrol.js
+++ b/addon/webextension/selector/uicontrol.js
@@ -3,7 +3,7 @@
 
 "use strict";
 
-window.uicontrol = (function () {
+this.uicontrol = (function () {
   let exports = {};
 
   /**********************************************************
diff --git a/addon/webextension/selector/util.js b/addon/webextension/selector/util.js
index a834526d54..19dc576a72 100644
--- a/addon/webextension/selector/util.js
+++ b/addon/webextension/selector/util.js
@@ -1,6 +1,6 @@
 "use strict";
 
-window.util = (function () { // eslint-disable-line no-unused-vars
+this.util = (function () { // eslint-disable-line no-unused-vars
   let exports = {};
 
   /** Removes a node from its document, if it's a node and the node is attached to a parent */
diff --git a/addon/webextension/sitehelper.js b/addon/webextension/sitehelper.js
index dfb0335df0..250a10352a 100644
--- a/addon/webextension/sitehelper.js
+++ b/addon/webextension/sitehelper.js
@@ -4,7 +4,7 @@
 
 "use strict";
 
-window.sitehelper = (function () {
+this.sitehelper = (function () {
 
   catcher.registerHandler((errorObj) => {
     callBackground("reportError", errorObj);
@@ -40,3 +40,4 @@ window.sitehelper = (function () {
   sendCustomEvent("addon-present");
 
 })();
+null;