diff --git a/flask/app.py b/flask/app.py
index c3bbc907..bfd615b7 100644
--- a/flask/app.py
+++ b/flask/app.py
@@ -1551,7 +1551,7 @@ class Flask(_PackageBoundObject):
             # set the headers and status.  We do this because there can be
             # some extra logic involved when creating these objects with
             # specific values (like default content type selection).
-            if isinstance(rv, string_types):
+            if isinstance(rv, string_types + (bytes, )):
                 rv = self.response_class(rv, headers=headers, status=status)
                 headers = status = None
             else:
diff --git a/flask/testsuite/appctx.py b/flask/testsuite/appctx.py
index 54b9014e..8524d22b 100644
--- a/flask/testsuite/appctx.py
+++ b/flask/testsuite/appctx.py
@@ -87,8 +87,9 @@ class AppContextTestCase(FlaskTestCase):
             with flask._app_ctx_stack.top:
                 with flask._request_ctx_stack.top:
                     pass
-            self.assert_true(flask._request_ctx_stack.request.environ
+            self.assert_true(flask._request_ctx_stack.top.request.environ
                 ['werkzeug.request'] is not None)
+            return u''
         c = app.test_client()
         c.get('/')
         self.assertEqual(called, ['request', 'app'])