--- a/toolkit/devtools/Loader.jsm
+++ b/toolkit/devtools/Loader.jsm
@@ -3,17 +3,28 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 "use strict";
 
 /**
  * Manages the addon-sdk loader instance used to load the developer tools.
  */
 
-let { classes: Cc, interfaces: Ci, utils: Cu } = Components;
+let { Constructor: CC, classes: Cc, interfaces: Ci, utils: Cu } = Components;
+
+// addDebuggerToGlobal only allows adding the Debugger object to a global. The
+// this object is not guaranteed to be a global (in particular on B2G, due to
+// compartment sharing), so add the Debugger object to a sandbox instead.
+let sandbox = Cu.Sandbox(CC('@mozilla.org/systemprincipal;1', 'nsIPrincipal')());
+Cu.evalInSandbox(
+  "Components.utils.import('resource://gre/modules/jsdebugger.jsm');" +
+  "addDebuggerToGlobal(this);",
+  sandbox
+);
+let Debugger = sandbox.Debugger;
 
 Cu.import("resource://gre/modules/XPCOMUtils.jsm");
 Cu.import("resource://gre/modules/Services.jsm");
 
 XPCOMUtils.defineLazyModuleGetter(this, "NetUtil", "resource://gre/modules/NetUtil.jsm");
 XPCOMUtils.defineLazyModuleGetter(this, "FileUtils", "resource://gre/modules/FileUtils.jsm");
 XPCOMUtils.defineLazyModuleGetter(this, "OS", "resource://gre/modules/osfile.jsm");
 XPCOMUtils.defineLazyModuleGetter(this, "console", "resource://gre/modules/devtools/Console.jsm");
@@ -46,16 +57,17 @@ let loaderGlobals = {
 };
 
 // Used when the tools should be loaded from the Firefox package itself (the default)
 function BuiltinProvider() {}
 BuiltinProvider.prototype = {
   load: function() {
     this.loader = new loader.Loader({
       modules: {
+        "Debugger": Debugger,
         "Services": Object.create(Services),
         "toolkit/loader": loader,
         "source-map": SourceMap,
       },
       paths: {
         // When you add a line to this mapping, don't forget to make a
         // corresponding addition to the SrcdirProvider mapping below as well.
         "": "resource://gre/modules/commonjs/",
@@ -123,16 +135,17 @@ SrcdirProvider.prototype = {
     let prettyFastURI = this.fileURI(OS.Path.join(toolkitDir), "pretty-fast.js");
     let asyncUtilsURI = this.fileURI(OS.Path.join(toolkitDir), "async-utils.js");
     let contentObserverURI = this.fileURI(OS.Path.join(toolkitDir), "content-observer.js");
     let gcliURI = this.fileURI(OS.Path.join(toolkitDir, "gcli", "source", "lib", "gcli"));
     let acornURI = this.fileURI(OS.Path.join(toolkitDir, "acorn"));
     let acornWalkURI = OS.Path.join(acornURI, "walk.js");
     this.loader = new loader.Loader({
       modules: {
+        "Debugger": Debugger,
         "Services": Object.create(Services),
         "toolkit/loader": loader,
         "source-map": SourceMap,
       },
       paths: {
         "": "resource://gre/modules/commonjs/",
         "main": mainURI,
         "devtools": devtoolsURI,

--- a/toolkit/devtools/server/main.js
+++ b/toolkit/devtools/server/main.js
@@ -4,50 +4,52 @@
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 "use strict";
 /**
  * Toolkit glue for the remote debugging protocol, loaded into the
  * debugging global.
  */
+let { Ci, Cc, CC, Cu, Cr } = require("chrome");
+let Debugger = require("Debugger");
+let Services = require("Services");
 let DevToolsUtils = require("devtools/toolkit/DevToolsUtils.js");
 let Services = require("Services");
 let EventEmitter = require("devtools/toolkit/event-emitter");
 
 // Until all Debugger server code is converted to SDK modules,
 // imports Components.* alias from chrome module.
 var { Ci, Cc, CC, Cu, Cr } = require("chrome");
 // On B2G, `this` != Global scope, so `Ci` won't be binded on `this`
 // (i.e. this.Ci is undefined) Then later, when using loadSubScript,
 // Ci,... won't be defined for sub scripts.
 this.Ci = Ci;
 this.Cc = Cc;
 this.CC = CC;
 this.Cu = Cu;
 this.Cr = Cr;
+this.Debugger = Debugger;
+this.Services = Services;
 this.DevToolsUtils = DevToolsUtils;
-this.Services = Services;
 
 // Overload `Components` to prevent SDK loader exception on Components
 // object usage
 Object.defineProperty(this, "Components", {
   get: function () require("chrome").components
 });
 
 const DBG_STRINGS_URI = "chrome://global/locale/devtools/debugger.properties";
 
 const nsFile = CC("@mozilla.org/file/local;1", "nsIFile", "initWithPath");
 Cu.import("resource://gre/modules/reflect.jsm");
 Cu.import("resource://gre/modules/XPCOMUtils.jsm");
 let wantLogging = Services.prefs.getBoolPref("devtools.debugger.log");
 
 Cu.import("resource://gre/modules/commonjs/sdk/core/promise.js");
-Cu.import("resource://gre/modules/jsdebugger.jsm");
-addDebuggerToGlobal(this);
 
 function loadSubScript(aURL)
 {
   try {
     let loader = Cc["@mozilla.org/moz/jssubscript-loader;1"]
       .getService(Ci.mozIJSSubScriptLoader);
     loader.loadSubScript(aURL, this);
   } catch(e) {