diff --git a/mercurial/filemerge.py b/mercurial/filemerge.py
--- a/mercurial/filemerge.py
+++ b/mercurial/filemerge.py
@@ -348,7 +348,9 @@
             return 0
         if premerge not in validkeep:
             # restore from backup and try again
-            util.copyfile(back, repo.wjoin(fcd.path()))
+            # TODO: Add a workingfilectx.write(otherfilectx) path so we can use
+            # util.copy here instead.
+            fcd.write(util.readfile(back), fcd.flags())
     return 1 # continue merging
 
 def _mergecheck(repo, mynode, orig, fcd, fco, fca, toolconf):
@@ -587,7 +589,7 @@
 
 def _makebackup(repo, ui, fcd, premerge):
     """Makes a backup of the local `fcd` file prior to merging.
-    
+
     In addition to preserving the user's pre-existing modifications to `fcd`
     (if any), the backup is used to undo certain premerges, confirm whether a
     merge changed anything, and determine what line endings the new file should