diff --git a/mercurial/copies.py b/mercurial/copies.py
--- a/mercurial/copies.py
+++ b/mercurial/copies.py
@@ -274,9 +274,10 @@
     * removed: a list of removed files
     """
     cl = repo.changelog
+    parents = cl._uncheckedparentrevs
 
     def revinfo(rev):
-        p1, p2 = cl.parentrevs(rev)
+        p1, p2 = parents(rev)
         ctx = repo[rev]
         p1copies, p2copies = ctx._copies
         removed = ctx.filesremoved()
@@ -292,11 +293,12 @@
     repo = a.repo()
     children = {}
     revinfo = _revinfogetter(repo)
+    parents = repo.changelog._uncheckedparentrevs
 
     cl = repo.changelog
     missingrevs = cl.findmissingrevs(common=[a.rev()], heads=[b.rev()])
     for r in missingrevs:
-        for p in cl.parentrevs(r):
+        for p in parents(r):
             if p == node.nullrev:
                 continue
             if p not in children: