diff --git a/hgext3rd/perftweaks.py b/hgext3rd/perftweaks.py
--- a/hgext3rd/perftweaks.py
+++ b/hgext3rd/perftweaks.py
@@ -287,6 +287,8 @@
 
 def _trackrebasesize(orig, self, dest, rebaseset):
     result = orig(self, dest, rebaseset)
+    if dest is None:
+        return result
 
     # The code assumes the rebase source is roughly a linear stack within a
     # single feature branch, and there is only one destination. If that is not
diff --git a/tests/test-perftweaks-remotenames.t b/tests/test-perftweaks-remotenames.t
--- a/tests/test-perftweaks-remotenames.t
+++ b/tests/test-perftweaks-remotenames.t
@@ -5,7 +5,9 @@
   > ssh=python "$TESTDIR/dummyssh"
   > [extensions]
   > perftweaks=$TESTDIR/../hgext3rd/perftweaks.py
+  > tweakdefaults=$TESTDIR/../hgext3rd/tweakdefaults.py
   > remotenames=
+  > rebase=
   > EOF
 
   $ hg init master
@@ -35,3 +37,13 @@
      default/master            0:cb9a9f314b8b
   $ cat .hg/remotenames
   cb9a9f314b8b07ba71012fcdbc544b5a4d82ff5b bookmarks default/master
+
+  $ hg pull --rebase -d master
+  pulling from ssh://user@dummy/master
+  searching for changes
+  adding changesets
+  adding manifests
+  adding file changes
+  added 1 changesets with 1 changes to 1 files
+  (run 'hg update' to get a working copy)
+  nothing to rebase - working directory parent is also destination