diff --git a/mercurial/copies.py b/mercurial/copies.py
--- a/mercurial/copies.py
+++ b/mercurial/copies.py
@@ -379,7 +379,9 @@
                         source = prev[1]
                     newcopies[dest] = (c, source)
                 assert newcopies is not copies
-            if changes is not None:
+            if changes is not None and changes.removed:
+                if newcopies is copies:
+                    newcopies = copies.copy()
                 for f in changes.removed:
                     if f in newcopies:
                         if newcopies is copies: