diff --git a/flake8/hooks.py b/flake8/hooks.py
index 7c7cd942..1a15f0b3 100644
--- a/flake8/hooks.py
+++ b/flake8/hooks.py
@@ -16,6 +16,11 @@
 from flake8.main import DEFAULT_CONFIG
 
 
+def fix_exclude(flake8_style, tmpdir):
+    flake8_style.options.exclude = [tmpdir + x if "/" in x else x
+                                    for x in flake8_style.options.exclude]
+
+
 def git_hook(complexity=-1, strict=False, ignore=None, lazy=False):
     """This is the function used by the git hook.
 
@@ -52,13 +57,7 @@ def git_hook(complexity=-1, strict=False, ignore=None, lazy=False):
 
     flake8_style = get_style_guide(config_file=DEFAULT_CONFIG, paths=['.'],
                                    **options)
-    # If an exclude pattern contains a slash, then pep8.read_config will
-    # convert it to an absolute path, using os.curdir as a base.  This behavior
-    # causes pep8.filename_match to fail, since our files will be
-    # in tmpdir, not os.curdir. The workaround below corrects this problem.
-    flake8_style.options.exclude = [tmpdir + x if "/" in x else x
-                                    for x in flake8_style.options.exclude]
-
+    fix_exclude(flake8_style, tmpdir)
     filepatterns = flake8_style.options.filename
 
     # Copy staged versions to temporary directory
diff --git a/flake8/tests/test_git_hook.py b/flake8/tests/test_git_hook.py
new file mode 100644
index 00000000..3efa4775
--- /dev/null
+++ b/flake8/tests/test_git_hook.py
@@ -0,0 +1,97 @@
+import unittest
+import mock
+
+import flake8.hooks
+import flake8.engine
+
+
+def side_effect(command, raw_output=False, decode=False):
+    if command.startswith("git diff-index") and not raw_output:
+        return 0, ["ignore.py", "myproject/main.py",
+                   "myproject/test/test.py"], []
+    elif command.startswith("git show") and raw_output:
+        return 0, "dummy standard output", "dummy standard error"
+    else:
+        raise NotImplementedError("side_effect")
+
+
+def mock_open(read_data=""):
+    #
+    # mock_open from older versions of mock do not have readline
+    #
+    # There is a patch for this issue (http://bugs.python.org/issue17467).
+    # I didn't use it directly since I needed readline to return None after all
+    # lines have been read. The multiple None objects appended at the end
+    # achieve this. I'm not sure why I need several -- one or two weren't
+    # enough.
+    #
+    mo = mock.mock_open(read_data=read_data)
+    lines = [x + "\n" for x in read_data.split("\n")] + [None]*10
+    mo.return_value.readline.side_effect = lines
+    return mo
+
+
+class TestFixExclude(unittest.TestCase):
+    """The scenario used to test fix_exclude is as follows.  There is a git
+    repo with two files: ignore.py, myproject/main.py and
+    myproject/test/test.py.  We want to run flake over myproject/main.py only.
+    To achieve this, we add myproject/test/test.py to the list of exclude
+    patterns -- in real life, this is done by editing configuration files
+    (http://flake8.readthedocs.org/en/latest/config.html), but for the test we
+    just mock it.
+
+    Without the fix, since the exclude pattern for test.py contains a slash,
+    pep8.read_config will convert it to an absolute path, using os.curdir as a
+    base.  This behavior causes pep8.filename_match to fail, since our files
+    will be in tmpdir, not os.curdir.  The end result is flake8 ends up
+    checking myproject/test/test.py, which is something we don't want.
+
+    With the fix, the exclude pattern is set correctly, and flake8 only checks
+    one file: myproject/main.py.
+
+    The exclude pattern for ignore.py is not affected by the fix, since it
+    doesn't contain a slash, and isn't converted to an absolute path by
+    pep8.read_config.
+    """
+
+    def setUp(self):
+        self.config = "[flake8]\nexclude = ignore.py,myproject/test/test.py"
+
+    @mock.patch("os.makedirs")
+    @mock.patch.object(flake8.engine.StyleGuide, "check_files")
+    @mock.patch("flake8.hooks.fix_exclude")
+    @mock.patch("flake8.hooks.mkdtemp", return_value="/tmp")
+    @mock.patch("flake8.hooks.run", side_effect=side_effect)
+    def test_without_fix(self, mock_run, mock_mkdtemp, mock_fix_exclude,
+                         mock_check_files, mock_makedirs):
+        #
+        # http://www.voidspace.org.uk/python/mock/helpers.html#mock.mock_open
+        #
+        with mock.patch("ConfigParser.open", mock_open(read_data=self.config),
+                        create=True):
+            with mock.patch("flake8.hooks.open", mock.mock_open(), create=True):
+                flake8.hooks.git_hook()
+
+        self.assertEquals(mock_check_files.call_count, 1)
+        args = mock_check_files.call_args[0][0]
+        print args
+        self.assertEquals(len(args), 2)
+
+    @mock.patch("os.makedirs")
+    @mock.patch.object(flake8.engine.StyleGuide, "check_files")
+    @mock.patch("flake8.hooks.mkdtemp", return_value="/tmp")
+    @mock.patch("flake8.hooks.run", side_effect=side_effect)
+    def test_with_fix(self, mock_run, mock_mkdtemp, mock_check_files,
+                      mock_makedirs):
+        #
+        # http://www.voidspace.org.uk/python/mock/helpers.html#mock.mock_open
+        #
+        with mock.patch("ConfigParser.open", mock_open(read_data=self.config),
+                        create=True):
+            with mock.patch("flake8.hooks.open", mock.mock_open(), create=True):
+                flake8.hooks.git_hook()
+
+        self.assertEquals(mock_check_files.call_count, 1)
+        args = mock_check_files.call_args[0][0]
+        print args
+        self.assertEquals(len(args), 1)