--- a/toolkit/components/social/FrameWorker.jsm
+++ b/toolkit/components/social/FrameWorker.jsm
@@ -125,16 +125,23 @@ FrameWorker.prototype = {
       appVersion: workerWindow.navigator.appVersion,
       platform: workerWindow.navigator.platform,
       userAgent: workerWindow.navigator.userAgent,
       // interface NavigatorOnLine
       get onLine() workerWindow.navigator.onLine
     };
     sandbox.navigator = navigator;
 
+    // Our importScripts function needs to 'eval' the script code from inside
+    // a function, but using eval() directly means functions in the script
+    // don't end up in the global scope.
+    sandbox._evalInSandbox = function(s) {
+      Cu.evalInSandbox(s, sandbox);
+    };
+
     // and we delegate ononline and onoffline events to the worker.
     // See http://www.whatwg.org/specs/web-apps/current-work/multipage/workers.html#workerglobalscope
     this.frame.addEventListener('offline', function fw_onoffline(event) {
       Cu.evalInSandbox("onoffline();", sandbox);
     }, false);
     this.frame.addEventListener('online', function fw_ononline(event) {
       Cu.evalInSandbox("ononline();", sandbox);
     }, false);

--- a/toolkit/components/social/MessagePortWorker.js
+++ b/toolkit/components/social/MessagePortWorker.js
@@ -27,17 +27,17 @@ function importScripts() {
   for (var i=0; i < arguments.length; i++) {
     // load the url *synchronously*
     var scriptURL = arguments[i];
     var xhr = new XMLHttpRequest();
     xhr.open('GET', scriptURL, false);
     xhr.onreadystatechange = function(aEvt) {
       if (xhr.readyState == 4) {
         if (xhr.status == 200 || xhr.status == 0) {
-          eval(xhr.responseText);
+          _evalInSandbox(xhr.responseText);
         }
         else {
           throw new Error("Unable to importScripts ["+scriptURL+"], status " + xhr.status)
         }
       }
     };
     xhr.send(null);
   }

--- a/toolkit/components/social/test/browser/relative_import.js
+++ b/toolkit/components/social/test/browser/relative_import.js
@@ -1,1 +1,6 @@
 dump("relative_import file\n");
+
+testVar = "oh hai";
+function testFunc() {
+  return "oh hai";
+}

--- a/toolkit/components/social/test/browser/worker_relative.js
+++ b/toolkit/components/social/test/browser/worker_relative.js
@@ -1,13 +1,18 @@
 // Used to test XHR in the worker.
 onconnect = function(e) {
   let port = e.ports[0];
   let req;
   try {
     importScripts("relative_import.js");
-    port.postMessage({topic: "done", result: "ok"});
+    // the import should have exposed "testVar" and "testFunc" from the module.
+    if (testVar == "oh hai" && testFunc() == "oh hai") {
+      port.postMessage({topic: "done", result: "ok"});
+    } else {
+      port.postMessage({topic: "done", result: "import worked but global is not available"});
+    }
   } catch(e) {
     port.postMessage({topic: "done", result: "FAILED to importScripts, " + e.toString() });
     return;
   }
   port.postMessage({topic: "done", result: "FAILED to importScripts, no exception" });
 }