diff --git a/flake8/_pyflakes.py b/flake8/_pyflakes.py
new file mode 100644
index 0000000..41189e0
--- /dev/null
+++ b/flake8/_pyflakes.py
@@ -0,0 +1,47 @@
+# -*- coding: utf-8 -*-
+import pyflakes
+import pyflakes.checker
+
+
+def patch_pyflakes():
+    """Add error codes to Pyflakes messages."""
+    codes = dict([line.split()[::-1] for line in (
+        'F401 UnusedImport',
+        'F402 ImportShadowedByLoopVar',
+        'F403 ImportStarUsed',
+        'F404 LateFutureImport',
+        'F810 Redefined',               # XXX Obsolete?
+        'F811 RedefinedWhileUnused',
+        'F812 RedefinedInListComp',
+        'F821 UndefinedName',
+        'F822 UndefinedExport',
+        'F823 UndefinedLocal',
+        'F831 DuplicateArgument',
+        'F841 UnusedVariable',
+    )])
+
+    for name, obj in vars(pyflakes.messages).items():
+        if name[0].isupper() and obj.message:
+            obj.flint_msg = '%s %s' % (codes.get(name, 'F999'), obj.message)
+patch_pyflakes()
+
+
+class FlakesChecker(pyflakes.checker.Checker):
+    """Subclass the Pyflakes checker to conform with the flint API."""
+    name = 'pyflakes'
+    version = pyflakes.__version__
+
+    @classmethod
+    def add_options(cls, parser):
+        parser.add_option('--builtins',
+                          help="define more built-ins, comma separated")
+        parser.config_options.append('builtins')
+
+    @classmethod
+    def parse_options(cls, options):
+        if options.builtins:
+            cls.builtIns = cls.builtIns.union(options.builtins.split(','))
+
+    def run(self):
+        for m in self.messages:
+            yield m.lineno, 0, (m.flint_msg % m.message_args), m.__class__
diff --git a/setup.py b/setup.py
index ad954df..8db2373 100644
--- a/setup.py
+++ b/setup.py
@@ -33,7 +33,10 @@ setup(
     ],
     entry_points={
         'distutils.commands': ['flake8 = flake8.main:Flake8Command'],
-        'console_scripts': ['flake8 = flake8.main:main']
+        'console_scripts': ['flake8 = flake8.main:main'],
+        'flake8.extension': [
+            'F = flake8._pyflakes:FlakesChecker',
+        ],
     },
     tests_require=['nose'],
     test_suite='nose.collector',