diff --git a/.hgsigs b/.hgsigs
--- a/.hgsigs
+++ b/.hgsigs
@@ -140,3 +140,4 @@ e69874dc1f4e142746ff3df91e678a09c6fc208c
 a1dd2c0c479e0550040542e392e87bc91262517e 0 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
 e1526da1e6d84e03146151c9b6e6950fe9a83d7d 0 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
 25703b624d27e3917d978af56d6ad59331e0464a 0 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
+ed5b25874d998ababb181a939dd37a16ea644435 0 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
diff --git a/.hgtags b/.hgtags
--- a/.hgtags
+++ b/.hgtags
@@ -153,3 +153,4 @@ e69874dc1f4e142746ff3df91e678a09c6fc208c
 a1dd2c0c479e0550040542e392e87bc91262517e 4.1-rc
 e1526da1e6d84e03146151c9b6e6950fe9a83d7d 4.1
 25703b624d27e3917d978af56d6ad59331e0464a 4.1.1
+ed5b25874d998ababb181a939dd37a16ea644435 4.1.2
diff --git a/mercurial/upgrade.py b/mercurial/upgrade.py
--- a/mercurial/upgrade.py
+++ b/mercurial/upgrade.py
@@ -524,14 +524,15 @@ def _upgraderepo(ui, srcrepo, dstrepo, r
                      'redeltamultibase' in actions)
 
     # Now copy other files in the store directory.
-    for p, kind, st in srcrepo.store.vfs.readdir('', stat=True):
+    # The sorted() makes execution deterministic.
+    for p, kind, st in sorted(srcrepo.store.vfs.readdir('', stat=True)):
         if not _filterstorefile(srcrepo, dstrepo, requirements,
                                        p, kind, st):
             continue
 
         srcrepo.ui.write(_('copying %s\n') % p)
-        src = srcrepo.store.vfs.join(p)
-        dst = dstrepo.store.vfs.join(p)
+        src = srcrepo.store.rawvfs.join(p)
+        dst = dstrepo.store.rawvfs.join(p)
         util.copyfile(src, dst, copystat=True)
 
     _finishdatamigration(ui, srcrepo, dstrepo, requirements)
diff --git a/tests/test-upgrade-repo.t b/tests/test-upgrade-repo.t
--- a/tests/test-upgrade-repo.t
+++ b/tests/test-upgrade-repo.t
@@ -310,3 +310,45 @@ old store should be backed up
   undo.phaseroots
 
   $ cd ..
+
+store files with special filenames aren't encoded during copy
+
+  $ hg init store-filenames
+  $ cd store-filenames
+  $ touch foo
+  $ hg -q commit -A -m initial
+  $ touch .hg/store/.XX_special_filename
+
+  $ hg debugupgraderepo --run
+  upgrade will perform the following actions:
+  
+  requirements
+     preserved: dotencode, fncache, generaldelta, revlogv1, store
+  
+  beginning upgrade...
+  repository locked and read-only
+  creating temporary repository to stage migrated data: $TESTTMP/store-filenames/.hg/upgrade.* (glob)
+  (it is safe to interrupt this process any time before data migration completes)
+  migrating 3 total revisions (1 in filelogs, 1 in manifests, 1 in changelog)
+  migrating 109 bytes in store; 107 bytes tracked data
+  migrating 1 filelogs containing 1 revisions (0 bytes in store; 0 bytes tracked data)
+  finished migrating 1 filelog revisions across 1 filelogs; change in size: 0 bytes
+  migrating 1 manifests containing 1 revisions (46 bytes in store; 45 bytes tracked data)
+  finished migrating 1 manifest revisions across 1 manifests; change in size: 0 bytes
+  migrating changelog containing 1 revisions (63 bytes in store; 62 bytes tracked data)
+  finished migrating 1 changelog revisions; change in size: 0 bytes
+  finished migrating 3 total revisions; total change in store size: 0 bytes
+  copying .XX_special_filename
+  copying phaseroots
+  data fully migrated to temporary repository
+  marking source repository as being upgraded; clients will be unable to read from repository
+  starting in-place swap of repository data
+  replaced files will be backed up at $TESTTMP/store-filenames/.hg/upgradebackup.* (glob)
+  replacing store...
+  store replacement complete; repository was inconsistent for *s (glob)
+  finalizing requirements file and making repository readable again
+  removing temporary repository $TESTTMP/store-filenames/.hg/upgrade.* (glob)
+  copy of old repository backed up at $TESTTMP/store-filenames/.hg/upgradebackup.* (glob)
+  the old repository will not be deleted; remove it to free up disk space once the upgraded repository is verified
+
+  $ cd ..