diff --git a/toolkit/components/osfile/modules/osfile_async_front.jsm b/toolkit/components/osfile/modules/osfile_async_front.jsm
index a763cfba879..e7e5ea527c0 100644
--- a/toolkit/components/osfile/modules/osfile_async_front.jsm
+++ b/toolkit/components/osfile/modules/osfile_async_front.jsm
@@ -208,9 +208,16 @@ let Scheduler = {
         // Decode any serialized error
         if (error instanceof PromiseWorker.WorkerError) {
           throw OS.File.Error.fromMsg(error.data);
-        } else {
-          throw error;
         }
+        // Extract something meaningful from WorkerErrorEvent
+        if (typeof error == "object" && error && error.constructor.name == "WorkerErrorEvent") {
+          let message = error.message;
+          if (message == "uncaught exception: [object StopIteration]") {
+            throw StopIteration;
+          }
+          throw new Error(message, error.filename, error.lineno);
+        }
+        throw error;
       }
     );
   }
@@ -965,14 +972,11 @@ DirectoryIterator.prototype = {
     promise = promise.then(
       DirectoryIterator.Entry.fromMsg,
       function onReject(reason) {
-        // If the exception is |StopIteration| (which we may determine only
-        // from its message...) we need to stop the iteration.
-        if (!(reason instanceof WorkerErrorEvent && reason.message == "uncaught exception: [object StopIteration]")) {
-          // Any exception other than StopIteration should be propagated as such
-          throw reason;
+        if (reason == StopIteration) {
+          self.close();
+          throw StopIteration;
         }
-        self.close();
-        throw StopIteration;
+        throw reason;
       });
     return promise;
   },
diff --git a/toolkit/components/osfile/tests/xpcshell/test_exception.js b/toolkit/components/osfile/tests/xpcshell/test_exception.js
new file mode 100644
index 00000000000..e28950fb1d9
--- /dev/null
+++ b/toolkit/components/osfile/tests/xpcshell/test_exception.js
@@ -0,0 +1,29 @@
+/* Any copyright is dedicated to the Public Domain.
+ * http://creativecommons.org/publicdomain/zero/1.0/ */
+
+"use strict";
+
+Components.utils.import("resource://gre/modules/osfile.jsm");
+
+function run_test() {
+  do_test_pending();
+  run_next_test();
+}
+
+add_task(function test_typeerror() {
+  let exn;
+  try {
+    let fd = yield OS.File.open("/tmp", {no_such_key: 1});
+    do_print("Fd: " + fd);
+  } catch (ex) {
+    exn = ex;
+  }
+  do_print("Exception: " + exn);
+  do_check_true(typeof exn == "object");
+  do_check_true("name" in exn);
+  do_check_true(exn.message.indexOf("TypeError") != -1);
+});
+
+add_task(function() {
+  do_test_finished();
+});
diff --git a/toolkit/components/osfile/tests/xpcshell/xpcshell.ini b/toolkit/components/osfile/tests/xpcshell/xpcshell.ini
index 97655c3cdd6..c9ac7cc8350 100644
--- a/toolkit/components/osfile/tests/xpcshell/xpcshell.ini
+++ b/toolkit/components/osfile/tests/xpcshell/xpcshell.ini
@@ -8,5 +8,6 @@ tail =
 [test_profiledir.js]
 [test_logging.js]
 [test_creationDate.js]
+[test_exception.js]
 [test_path_constants.js]
 [test_removeDir.js]