diff --git a/checkout.py b/checkout.py
index 09ea9c3fa..9f21acc90 100644
--- a/checkout.py
+++ b/checkout.py
@@ -59,7 +59,12 @@ class CheckoutBase(object):
   # Set to None to have verbose output.
   VOID = subprocess2.VOID
 
-  def __init__(self, root_dir, project_name):
+  def __init__(self, root_dir, project_name, post_processors):
+    """
+    Args:
+      post_processor: list of lambda(checkout, patches) to call on each of the
+                      modified files.
+    """
     self.root_dir = root_dir
     self.project_name = project_name
     if self.project_name is None:
@@ -68,6 +73,7 @@ class CheckoutBase(object):
       self.project_path = os.path.join(self.root_dir, self.project_name)
     # Only used for logging purposes.
     self._last_seen_revision = None
+    self.post_processors = None
     assert self.root_dir
     assert self.project_path
 
@@ -82,7 +88,7 @@ class CheckoutBase(object):
     """
     raise NotImplementedError()
 
-  def apply_patch(self, patches, post_processor=None):
+  def apply_patch(self, patches):
     """Applies a patch and returns the list of modified files.
 
     This function should throw patch.UnsupportedPatchFormat or
@@ -90,8 +96,6 @@ class CheckoutBase(object):
 
     Args:
       patches: patch.PatchSet object.
-      post_processor: list of lambda(checkout, patches) to call on each of the
-                      modified files.
     """
     raise NotImplementedError()
 
@@ -109,9 +113,8 @@ class RawCheckout(CheckoutBase):
     """Stubbed out."""
     pass
 
-  def apply_patch(self, patches, post_processor=None):
+  def apply_patch(self, patches):
     """Ignores svn properties."""
-    post_processor = post_processor or []
     for p in patches:
       try:
         stdout = ''
@@ -137,7 +140,7 @@ class RawCheckout(CheckoutBase):
             elif p.is_new and not os.path.exists(filepath):
               # There is only a header. Just create the file.
               open(filepath, 'w').close()
-        for post in post_processor:
+        for post in (self.post_processors or []):
           post(self, p)
       except OSError, e:
         raise PatchApplicationFailed(p.filename, '%s%s' % (stdout, e))
@@ -233,8 +236,9 @@ class SvnMixIn(object):
 
 class SvnCheckout(CheckoutBase, SvnMixIn):
   """Manages a subversion checkout."""
-  def __init__(self, root_dir, project_name, commit_user, commit_pwd, svn_url):
-    super(SvnCheckout, self).__init__(root_dir, project_name)
+  def __init__(self, root_dir, project_name, commit_user, commit_pwd, svn_url,
+      post_processors=None):
+    super(SvnCheckout, self).__init__(root_dir, project_name, post_processors)
     self.commit_user = commit_user
     self.commit_pwd = commit_pwd
     self.svn_url = svn_url
@@ -252,8 +256,7 @@ class SvnCheckout(CheckoutBase, SvnMixIn):
       self._last_seen_revision = revision
     return revision
 
-  def apply_patch(self, patches, post_processor=None):
-    post_processor = post_processor or []
+  def apply_patch(self, patches):
     for p in patches:
       try:
         # It is important to use credentials=False otherwise credentials could
@@ -306,7 +309,7 @@ class SvnCheckout(CheckoutBase, SvnMixIn):
                   params = value.split('=', 1)
                 stdout += self._check_output_svn(
                     ['propset'] + params + [p.filename], credentials=False)
-        for post in post_processor:
+        for post in (self.post_processors or []):
           post(self, p)
       except OSError, e:
         raise PatchApplicationFailed(p.filename, '%s%s' % (stdout, e))
@@ -369,8 +372,10 @@ class SvnCheckout(CheckoutBase, SvnMixIn):
 
 class GitCheckoutBase(CheckoutBase):
   """Base class for git checkout. Not to be used as-is."""
-  def __init__(self, root_dir, project_name, remote_branch):
-    super(GitCheckoutBase, self).__init__(root_dir, project_name)
+  def __init__(self, root_dir, project_name, remote_branch,
+      post_processors=None):
+    super(GitCheckoutBase, self).__init__(
+        root_dir, project_name, post_processors)
     # There is no reason to not hardcode it.
     self.remote = 'origin'
     self.remote_branch = remote_branch
@@ -391,14 +396,13 @@ class GitCheckoutBase(CheckoutBase):
     if self.working_branch in branches:
       self._call_git(['branch', '-D', self.working_branch])
 
-  def apply_patch(self, patches, post_processor=None):
+  def apply_patch(self, patches):
     """Applies a patch on 'working_branch' and switch to it.
 
     Also commits the changes on the local branch.
 
     Ignores svn properties and raise an exception on unexpected ones.
     """
-    post_processor = post_processor or []
     # It this throws, the checkout is corrupted. Maybe worth deleting it and
     # trying again?
     if self.remote_branch:
@@ -435,7 +439,7 @@ class GitCheckoutBase(CheckoutBase):
                   p.filename,
                   'Cannot apply svn property %s to file %s.' % (
                         prop[0], p.filename))
-        for post in post_processor:
+        for post in (self.post_processors or []):
           post(self, p)
       except OSError, e:
         raise PatchApplicationFailed(p.filename, '%s%s' % (stdout, e))
@@ -492,10 +496,10 @@ class GitSvnCheckoutBase(GitCheckoutBase, SvnMixIn):
   def __init__(self,
       root_dir, project_name, remote_branch,
       commit_user, commit_pwd,
-      svn_url, trunk):
+      svn_url, trunk, post_processors=None):
     """trunk is optional."""
     super(GitSvnCheckoutBase, self).__init__(
-        root_dir, project_name + '.git', remote_branch)
+        root_dir, project_name + '.git', remote_branch, post_processors)
     self.commit_user = commit_user
     self.commit_pwd = commit_pwd
     # svn_url in this case is the root of the svn repository.
@@ -583,11 +587,11 @@ class GitSvnPremadeCheckout(GitSvnCheckoutBase):
   def __init__(self,
       root_dir, project_name, remote_branch,
       commit_user, commit_pwd,
-      svn_url, trunk, git_url):
+      svn_url, trunk, git_url, post_processors=None):
     super(GitSvnPremadeCheckout, self).__init__(
         root_dir, project_name, remote_branch,
         commit_user, commit_pwd,
-        svn_url, trunk)
+        svn_url, trunk, post_processors)
     self.git_url = git_url
     assert self.git_url
 
@@ -627,11 +631,11 @@ class GitSvnCheckout(GitSvnCheckoutBase):
   def __init__(self,
       root_dir, project_name,
       commit_user, commit_pwd,
-      svn_url, trunk):
+      svn_url, trunk, post_processors=None):
     super(GitSvnCheckout, self).__init__(
         root_dir, project_name, 'trunk',
         commit_user, commit_pwd,
-        svn_url, trunk)
+        svn_url, trunk, post_processors)
 
   def prepare(self):
     """Creates the initial checkout for the repo."""
@@ -663,8 +667,8 @@ class ReadOnlyCheckout(object):
   def get_settings(self, key):
     return self.checkout.get_settings(key)
 
-  def apply_patch(self, patches, post_processor=None):
-    return self.checkout.apply_patch(patches, post_processor)
+  def apply_patch(self, patches):
+    return self.checkout.apply_patch(patches)
 
   def commit(self, message, user):  # pylint: disable=R0201
     logging.info('Would have committed for %s with message: %s' % (
diff --git a/tests/checkout_test.py b/tests/checkout_test.py
index 59a3f529a..4ea73a06e 100755
--- a/tests/checkout_test.py
+++ b/tests/checkout_test.py
@@ -236,10 +236,11 @@ class BaseTest(fake_repos.FakeReposTestBase):
 
   def _test_process(self, co):
     """Makes sure the process lambda is called correctly."""
+    co.post_processors = [lambda *args: results.append(args)]
     co.prepare()
     ps = self.get_patches()
     results = []
-    co.apply_patch(ps, [lambda *args: results.append(args)])
+    co.apply_patch(ps)
     expected = [(co, p) for p in ps.patches]
     self.assertEquals(expected, results)
 
@@ -479,7 +480,7 @@ class RawCheckout(SvnBaseTest):
     self.base_co.prepare()
 
   def _get_co(self, read_only):
-    co = checkout.RawCheckout(self.root_dir, self.name)
+    co = checkout.RawCheckout(self.root_dir, self.name, None)
     if read_only:
       return checkout.ReadOnlyCheckout(co)
     return co