diff --git a/setup.py b/setup.py
--- a/setup.py
+++ b/setup.py
@@ -5,14 +5,15 @@
 # './setup.py install', or
 # './setup.py --help' for more options
 
-from distutils.core import setup
+from distutils.core import setup, Extension
 
 setup(name='mercurial',
-            version='0.4f',
-            author='Matt Mackall',
-            author_email='mpm@selenic.com',
-            url='http://selenic.com/mercurial',
-            description='scalable distributed SCM',
-            license='GNU GPL',
-            packages=['mercurial'],
-            scripts=['hg', 'hgweb.py'])
+      version='0.4f',
+      author='Matt Mackall',
+      author_email='mpm@selenic.com',
+      url='http://selenic.com/mercurial',
+      description='scalable distributed SCM',
+      license='GNU GPL',
+      packages=['mercurial'],
+      ext_modules=[Extension('mercurial.mpatch', ['mercurial/mpatch.c'])],
+      scripts=['hg', 'hgweb.py'])