diff --git a/kallithea/lib/diffs.py b/kallithea/lib/diffs.py
--- a/kallithea/lib/diffs.py
+++ b/kallithea/lib/diffs.py
@@ -364,7 +364,7 @@ class DiffProcessor(object):
         groups = match.groupdict()
         rest = diff_chunk[match.end():]
         if rest and not rest.startswith('@') and not rest.startswith('literal ') and not rest.startswith('delta '):
-            raise Exception('cannot parse diff header: %r followed by %r' % (diff_chunk[:match.end()], rest[:1000]))
+            raise Exception('cannot parse %s diff header: %r followed by %r' % (self.vcs, diff_chunk[:match.end()], rest[:1000]))
         difflines = imap(self._escaper, re.findall(r'.*\n|.+$', rest)) # don't split on \r as str.splitlines do
         return groups, difflines
 
diff --git a/kallithea/tests/models/test_diff_parsers.py b/kallithea/tests/models/test_diff_parsers.py
--- a/kallithea/tests/models/test_diff_parsers.py
+++ b/kallithea/tests/models/test_diff_parsers.py
@@ -276,7 +276,10 @@ class DiffLibTest(BaseTestCase):
     @parameterized.expand([(x,) for x in DIFF_FIXTURES])
     def test_diff(self, diff_fixture):
         diff = fixture.load_resource(diff_fixture, strip=False)
-        diff_proc = DiffProcessor(diff)
+        vcs = 'hg'
+        if diff_fixture.startswith('git_'):
+            vcs = 'git'
+        diff_proc = DiffProcessor(diff, vcs=vcs)
         diff_proc_d = diff_proc.prepare()
         data = [(x['filename'], x['operation'], x['stats']) for x in diff_proc_d]
         expected_data = DIFF_FIXTURES[diff_fixture]