diff --git a/flask/ext/__init__.py b/flask/ext/__init__.py
index 86ad3da5..1eda6df5 100644
--- a/flask/ext/__init__.py
+++ b/flask/ext/__init__.py
@@ -57,6 +57,17 @@ class _ExtensionImporter(object):
                 __import__(realname)
             except ImportError:
                 exc_type, exc_value, tb = exc_info()
+                # since we only establish the entry in sys.modules at the
+                # very this seems to be redundant, but if recursive imports
+                # happen we will call into the move import a second time.
+                # On the second invocation we still don't have an entry for
+                # fullname in sys.modules, but we will end up with the same
+                # fake module name and that import will succeed since this
+                # one already has a temporary entry in the modules dict.
+                # Since this one "succeeded" temporarily that second
+                # invocation now will have created a fullname entry in
+                # sys.modules which we have to kill.
+                modules.pop(fullname, None)
                 if self.is_important_traceback(realname, tb):
                     raise exc_type, exc_value, tb
                 continue
diff --git a/flask/testsuite/__init__.py b/flask/testsuite/__init__.py
index 49b85b23..9f9e0a60 100644
--- a/flask/testsuite/__init__.py
+++ b/flask/testsuite/__init__.py
@@ -134,6 +134,32 @@ class FlaskTestCase(unittest.TestCase):
     def assert_equal(self, x, y):
         return self.assertEqual(x, y)
 
+    def assert_raises(self, exc_type, callable=None, *args, **kwargs):
+        catcher = _ExceptionCatcher(self, exc_type)
+        if callable is None:
+            return catcher
+        with catcher:
+            callable(*args, **kwargs)
+
+
+class _ExceptionCatcher(object):
+
+    def __init__(self, test_case, exc_type):
+        self.test_case = test_case
+        self.exc_type = exc_type
+
+    def __enter__(self):
+        return self
+
+    def __exit__(self, exc_type, exc_value, tb):
+        exception_name = self.exc_type.__name__
+        if exc_type is None:
+            self.test_case.fail('Expected exception of type %r' %
+                                exception_name)
+        elif not issubclass(exc_type, self.exc_type):
+            raise exc_type, exc_value, tb
+        return True
+
 
 class BetterLoader(unittest.TestLoader):
     """A nicer loader that solves two problems.  First of all we are setting
diff --git a/flask/testsuite/ext.py b/flask/testsuite/ext.py
index dc90952f..966db439 100644
--- a/flask/testsuite/ext.py
+++ b/flask/testsuite/ext.py
@@ -8,6 +8,8 @@
     :copyright: (c) 2011 by Armin Ronacher.
     :license: BSD, see LICENSE for more details.
 """
+from __future__ import with_statement
+
 import sys
 import unittest
 from flask.testsuite import FlaskTestCase
@@ -92,6 +94,11 @@ class ExtImportHookTestCase(FlaskTestCase):
         from flask.ext.oldext_package.submodule import test_function
         self.assert_equal(test_function(), 42)
 
+    def test_flaskext_broken_package_no_module_caching(self):
+        for x in xrange(2):
+            with self.assert_raises(ImportError):
+                import flask.ext.broken
+
 
 def suite():
     suite = unittest.TestSuite()
diff --git a/flask/testsuite/test_apps/flask_broken/__init__.py b/flask/testsuite/test_apps/flask_broken/__init__.py
new file mode 100644
index 00000000..c194c04f
--- /dev/null
+++ b/flask/testsuite/test_apps/flask_broken/__init__.py
@@ -0,0 +1,2 @@
+import flask.ext.broken.b
+import missing_module
diff --git a/flask/testsuite/test_apps/flask_broken/b.py b/flask/testsuite/test_apps/flask_broken/b.py
new file mode 100644
index 00000000..e69de29b
diff --git a/scripts/flaskext_compat.py b/scripts/flaskext_compat.py
index f0b1739d..bb3ada03 100644
--- a/scripts/flaskext_compat.py
+++ b/scripts/flaskext_compat.py
@@ -25,7 +25,8 @@ ext_module.__package__ = ext_module.__name__
 
 class _ExtensionImporter(object):
     """This importer redirects imports from the flask.ext module to other
-    locations.
+    locations.  For implementation details see the code in Flask 0.8
+    that does the same.
     """
     _module_choices = ['flask_%s', 'flaskext.%s']
     prefix = ext_module.__name__ + '.'
@@ -45,6 +46,7 @@ class _ExtensionImporter(object):
                 __import__(realname)
             except ImportError:
                 exc_type, exc_value, tb = sys.exc_info()
+                sys.modules.pop(fullname, None)
                 if self.is_important_traceback(realname, tb):
                     raise exc_type, exc_value, tb
                 continue
@@ -55,12 +57,6 @@ class _ExtensionImporter(object):
         raise ImportError('No module named %s' % fullname)
 
     def is_important_traceback(self, important_module, tb):
-        """Walks a traceback's frames and checks if any of the frames
-        originated in the given important module.  If that is the case
-        then we were able to import the module itself but apparently
-        something went wrong when the module was imported.  (Eg: import
-        of an import failed).
-        """
         while tb is not None:
             if tb.tb_frame.f_globals.get('__name__') == important_module:
                 return True