diff --git a/otterwiki/gitstorage.py b/otterwiki/gitstorage.py
index 8fa5874..d9ccbf1 100644
--- a/otterwiki/gitstorage.py
+++ b/otterwiki/gitstorage.py
@@ -268,9 +268,9 @@ def revert(self, revision, message="", author=("","")):
         actor = git.Actor(author[0], author[1])
         self.repo.index.commit(message, author=actor)
 
-    def diff(self, filename, rev_a, rev_b):
+    def diff(self, rev_a, rev_b):
         # https://docs.python.org/2/library/difflib.html
-        return self.repo.git.diff(rev_a, rev_b, filename)
+        return self.repo.git.diff(rev_a, rev_b)
 
     def delete(self, filename, message=None, author=("","")):
         if not type(filename) == list:
diff --git a/tests/test_gitstorage.py b/tests/test_gitstorage.py
index 023b2a5..bbb66f8 100644
--- a/tests/test_gitstorage.py
+++ b/tests/test_gitstorage.py
@@ -301,7 +301,7 @@ def test_diff(storage):
     # get revisions
     rev_b, rev_a = log[0]["revision"], log[1]["revision"]
     # get diff
-    diff = storage.diff(filename, rev_a, rev_b)
+    diff = storage.diff(rev_a, rev_b)
     # check -/+ strings
     assert "-aaa" in diff
     assert "+bbb" in diff