diff --git a/mypy/version.py b/mypy/version.py
index 9c836b031cb52..091e99bec7f55 100644
--- a/mypy/version.py
+++ b/mypy/version.py
@@ -1 +1,11 @@
+import os
+from mypy import git
+
 __version__ = '0.4.6-dev'
+
+mypy_dir = os.path.abspath(os.path.dirname(os.path.dirname(__file__)))
+if git.is_git_repo(mypy_dir) and git.have_git():
+    __version__ += '-' + git.git_revision(mypy_dir).decode('utf-8')
+    if git.is_dirty(mypy_dir):
+        __version__ += '-dirty'
+del mypy_dir
diff --git a/setup.py b/setup.py
index 3733f72800c62..f9c249fb7b984 100644
--- a/setup.py
+++ b/setup.py
@@ -31,19 +31,6 @@
 '''.lstrip()
 
 
-def cache_version_id():
-    """Returns the version id to use for the incremental hash.
-
-    If setup.py is run from a git repo, the git commit hash will be
-    included if possible. If not, then this function will fall back to
-    using the default version id from mypy/version.py."""
-    if git.is_git_repo('.') and git.have_git():
-        return __version__ + '-' + git.git_revision('.').decode('utf-8')
-    else:
-        # Default fallback
-        return __version__
-
-
 def find_data_files(base, globs):
     """Find all interesting data files, for setup(data_files=)
 
@@ -71,7 +58,7 @@ def pin_version(self):
         path = os.path.join(self.build_lib, 'mypy')
         self.mkpath(path)
         with open(os.path.join(path, 'version.py'), 'w') as stream:
-            stream.write('__version__ = "{}"\n'.format(cache_version_id()))
+            stream.write('__version__ = "{}"\n'.format(version))
 
     def run(self):
         self.execute(self.pin_version, ())