diff --git a/dom/base/FileReader.cpp b/dom/base/FileReader.cpp
index 62741c40fc8..b3daf1eab8c 100644
--- a/dom/base/FileReader.cpp
+++ b/dom/base/FileReader.cpp
@@ -98,9 +98,9 @@ FileReader::RootResultArrayBuffer()
 
 //FileReader constructors/initializers
 
-FileReader::FileReader(nsPIDOMWindow* aWindow,
+FileReader::FileReader(nsIGlobalObject* aGlobal,
                        WorkerPrivate* aWorkerPrivate)
-  : DOMEventTargetHelper(aWindow)
+  : DOMEventTargetHelper(aGlobal)
   , mFileData(nullptr)
   , mDataLen(0)
   , mDataFormat(FILE_AS_BINARY)
@@ -114,8 +114,8 @@ FileReader::FileReader(nsPIDOMWindow* aWindow,
   , mBusyCount(0)
   , mWorkerPrivate(aWorkerPrivate)
 {
-  MOZ_ASSERT_IF(!NS_IsMainThread(), mWorkerPrivate && !aWindow);
-  MOZ_ASSERT_IF(NS_IsMainThread(), !mWorkerPrivate);
+  MOZ_ASSERT(aGlobal);
+  MOZ_ASSERT(NS_IsMainThread() == !mWorkerPrivate);
   SetDOMStringToNull(mResult);
 }
 
@@ -128,8 +128,7 @@ FileReader::~FileReader()
 /* static */ already_AddRefed<FileReader>
 FileReader::Constructor(const GlobalObject& aGlobal, ErrorResult& aRv)
 {
-  // The owner can be null when this object is used by chrome code.
-  nsCOMPtr<nsPIDOMWindow> owner = do_QueryInterface(aGlobal.GetAsSupports());
+  nsCOMPtr<nsIGlobalObject> global = do_QueryInterface(aGlobal.GetAsSupports());
   WorkerPrivate* workerPrivate = nullptr;
 
   if (!NS_IsMainThread()) {
@@ -138,14 +137,7 @@ FileReader::Constructor(const GlobalObject& aGlobal, ErrorResult& aRv)
     MOZ_ASSERT(workerPrivate);
   }
 
-  RefPtr<FileReader> fileReader = new FileReader(owner, workerPrivate);
-
-  if (!owner && nsContentUtils::ThreadsafeIsCallerChrome()) {
-    // Instead of grabbing some random global from the context stack,
-    // let's use the default one (junk scope) for now.
-    // We should move away from this Init...
-    fileReader->BindToOwner(xpc::NativeGlobal(xpc::PrivilegedJunkScope()));
-  }
+  RefPtr<FileReader> fileReader = new FileReader(global, workerPrivate);
 
   return fileReader.forget();
 }
@@ -242,17 +234,7 @@ FileReader::DoOnLoadEnd(nsresult aStatus,
   switch (mDataFormat) {
     case FILE_AS_ARRAYBUFFER: {
       AutoJSAPI jsapi;
-      nsCOMPtr<nsIGlobalObject> globalObject;
-
-      if (NS_IsMainThread()) {
-        globalObject = do_QueryInterface(GetParentObject());
-      } else {
-        MOZ_ASSERT(mWorkerPrivate);
-        MOZ_ASSERT(mBusyCount);
-        globalObject = mWorkerPrivate->GlobalScope();
-      }
-
-      if (!globalObject || !jsapi.Init(globalObject)) {
+      if (!jsapi.Init(GetParentObject())) {
         FreeFileData();
         return NS_ERROR_FAILURE;
       }
diff --git a/dom/base/FileReader.h b/dom/base/FileReader.h
index ab733ff39c7..693c87ee739 100644
--- a/dom/base/FileReader.h
+++ b/dom/base/FileReader.h
@@ -46,7 +46,7 @@ class FileReader final : public DOMEventTargetHelper,
   friend class FileReaderDecreaseBusyCounter;
 
 public:
-  FileReader(nsPIDOMWindow* aWindow,
+  FileReader(nsIGlobalObject* aGlobal,
              workers::WorkerPrivate* aWorkerPrivate);
 
   NS_DECL_ISUPPORTS_INHERITED
diff --git a/dom/workers/test/xpcshell/data/worker_fileReader.js b/dom/workers/test/xpcshell/data/worker_fileReader.js
new file mode 100644
index 00000000000..b27366d17ba
--- /dev/null
+++ b/dom/workers/test/xpcshell/data/worker_fileReader.js
@@ -0,0 +1,8 @@
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+
+self.onmessage = function(msg) {
+  var fr = new FileReader();
+  self.postMessage("OK");
+};
diff --git a/dom/workers/test/xpcshell/test_fileReader.js b/dom/workers/test/xpcshell/test_fileReader.js
new file mode 100644
index 00000000000..0e283fbe017
--- /dev/null
+++ b/dom/workers/test/xpcshell/test_fileReader.js
@@ -0,0 +1,40 @@
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+Components.utils.import("resource://gre/modules/Promise.jsm");
+
+// Worker must be loaded from a chrome:// uri, not a file://
+// uri, so we first need to load it.
+var WORKER_SOURCE_URI = "chrome://workers/content/worker_fileReader.js";
+do_load_manifest("data/chrome.manifest");
+
+function run_test() {
+  run_next_test();
+}
+
+function talk_with_worker(worker) {
+  let deferred = Promise.defer();
+  worker.onmessage = function(event) {
+    let success = true;
+    if (event.data == "OK") {
+      deferred.resolve();
+    } else {
+      success = false;
+      deferred.reject(event);
+    }
+    do_check_true(success);
+    worker.terminate();
+  };
+  worker.onerror = function(event) {
+    let error = new Error(event.message, event.filename, event.lineno);
+    worker.terminate();
+    deferred.reject(error);
+  };
+  worker.postMessage("START");
+  return deferred.promise;
+}
+
+
+add_task(function test_chrome_worker() {
+  return talk_with_worker(new ChromeWorker(WORKER_SOURCE_URI));
+});
diff --git a/dom/workers/test/xpcshell/xpcshell.ini b/dom/workers/test/xpcshell/xpcshell.ini
index f1437f9ac79..698fca76eeb 100644
--- a/dom/workers/test/xpcshell/xpcshell.ini
+++ b/dom/workers/test/xpcshell/xpcshell.ini
@@ -4,6 +4,8 @@ tail =
 skip-if = toolkit == 'android' || toolkit == 'gonk'
 support-files =
   data/worker.js
+  data/worker_fileReader.js
   data/chrome.manifest
 
 [test_workers.js]
+[test_fileReader.js]