diff --git a/flask/testsuite/config.py b/flask/testsuite/config.py
index e0f7005f..00f77cea 100644
--- a/flask/testsuite/config.py
+++ b/flask/testsuite/config.py
@@ -8,10 +8,14 @@
     :copyright: (c) 2011 by Armin Ronacher.
     :license: BSD, see LICENSE for more details.
 """
+from __future__ import with_statement
+
 import os
 import sys
 import flask
+import pkgutil
 import unittest
+from contextlib import contextmanager
 from flask.testsuite import FlaskTestCase
 
 
@@ -84,6 +88,35 @@ class ConfigTestCase(FlaskTestCase):
         self.assert_equal(app.permanent_session_lifetime.seconds, 42)
 
 
+class LimitedLoaderMockWrapper(object):
+    def __init__(self, loader):
+        self.loader = loader
+
+    def __getattr__(self, name):
+        if name in ('archive', 'get_filename'):
+            msg = 'Mocking a loader which does not have `%s.`' % name
+            raise AttributeError, msg
+        return getattr(self.loader, name)
+
+
+@contextmanager
+def patch_pkgutil_get_loader(wrapper_class=LimitedLoaderMockWrapper):
+    """Patch pkgutil.get_loader to give loader without get_filename or archive.
+
+    This provides for tests where a system has custom loaders, e.g. Google App
+    Engine's HardenedModulesHook, which have neither the `get_filename` method
+    nor the `archive` attribute.
+    """
+    old_get_loader = pkgutil.get_loader
+    def get_loader(*args, **kwargs):
+        return wrapper_class(old_get_loader(*args, **kwargs))
+    try:
+        pkgutil.get_loader = get_loader
+        yield
+    finally:
+        pkgutil.get_loader = old_get_loader
+
+
 class InstanceTestCase(FlaskTestCase):
 
     def test_explicit_instance_paths(self):
@@ -133,6 +166,24 @@ class InstanceTestCase(FlaskTestCase):
             if 'site_app' in sys.modules:
                 del sys.modules['site_app']
 
+    def test_installed_module_paths_with_limited_loader(self):
+        here = os.path.abspath(os.path.dirname(__file__))
+        expected_prefix = os.path.join(here, 'test_apps')
+        real_prefix, sys.prefix = sys.prefix, expected_prefix
+        site_packages = os.path.join(expected_prefix, 'lib', 'python2.5', 'site-packages')
+        sys.path.append(site_packages)
+        with patch_pkgutil_get_loader():
+            try:
+                import site_app
+                self.assert_equal(site_app.app.instance_path,
+                                  os.path.join(expected_prefix, 'var',
+                                               'site_app-instance'))
+            finally:
+                sys.prefix = real_prefix
+                sys.path.remove(site_packages)
+                if 'site_app' in sys.modules:
+                    del sys.modules['site_app']
+
     def test_installed_package_paths(self):
         here = os.path.abspath(os.path.dirname(__file__))
         expected_prefix = os.path.join(here, 'test_apps')
@@ -150,6 +201,24 @@ class InstanceTestCase(FlaskTestCase):
             if 'installed_package' in sys.modules:
                 del sys.modules['installed_package']
 
+    def test_installed_package_paths_with_limited_loader(self):
+        here = os.path.abspath(os.path.dirname(__file__))
+        expected_prefix = os.path.join(here, 'test_apps')
+        real_prefix, sys.prefix = sys.prefix, expected_prefix
+        installed_path = os.path.join(expected_prefix, 'path')
+        sys.path.append(installed_path)
+        with patch_pkgutil_get_loader():
+            try:
+                import installed_package
+                self.assert_equal(installed_package.app.instance_path,
+                                  os.path.join(expected_prefix, 'var',
+                                               'installed_package-instance'))
+            finally:
+                sys.prefix = real_prefix
+                sys.path.remove(installed_path)
+                if 'installed_package' in sys.modules:
+                    del sys.modules['installed_package']
+
     def test_prefix_package_paths(self):
         here = os.path.abspath(os.path.dirname(__file__))
         expected_prefix = os.path.join(here, 'test_apps')
@@ -167,6 +236,24 @@ class InstanceTestCase(FlaskTestCase):
             if 'site_package' in sys.modules:
                 del sys.modules['site_package']
 
+    def test_prefix_package_paths_with_limited_loader(self):
+        here = os.path.abspath(os.path.dirname(__file__))
+        expected_prefix = os.path.join(here, 'test_apps')
+        real_prefix, sys.prefix = sys.prefix, expected_prefix
+        site_packages = os.path.join(expected_prefix, 'lib', 'python2.5', 'site-packages')
+        sys.path.append(site_packages)
+        with patch_pkgutil_get_loader():
+            try:
+                import site_package
+                self.assert_equal(site_package.app.instance_path,
+                                  os.path.join(expected_prefix, 'var',
+                                               'site_package-instance'))
+            finally:
+                sys.prefix = real_prefix
+                sys.path.remove(site_packages)
+                if 'site_package' in sys.modules:
+                    del sys.modules['site_package']
+
     def test_egg_installed_paths(self):
         here = os.path.abspath(os.path.dirname(__file__))
         expected_prefix = os.path.join(here, 'test_apps')