diff --git a/mercurial/changelog.py b/mercurial/changelog.py
--- a/mercurial/changelog.py
+++ b/mercurial/changelog.py
@@ -305,7 +305,7 @@
         if self._changes is not None:
             return self._changes
         if self._cpsd:
-            changes = metadata.decode_files_sidedata(self, self._sidedata)
+            changes = metadata.decode_files_sidedata(self._sidedata)
         else:
             changes = metadata.ChangingFiles(
                 touched=self.files or (),
diff --git a/mercurial/metadata.py b/mercurial/metadata.py
--- a/mercurial/metadata.py
+++ b/mercurial/metadata.py
@@ -430,7 +430,7 @@
     return {sidedatamod.SD_FILES: b''.join(chunks)}
 
 
-def decode_files_sidedata(changelogrevision, sidedata):
+def decode_files_sidedata(sidedata):
     md = ChangingFiles()
     raw = sidedata.get(sidedatamod.SD_FILES)