mercurial/narrowspec.py

--- a/mercurial/narrowspec.py	Thu Aug 02 14:30:40 2018 -0700
+++ b/mercurial/narrowspec.py	Fri Aug 03 13:53:02 2018 -0700
@@ -137,7 +137,7 @@
 def restorebackup(repo, backupname):
     if repository.NARROW_REQUIREMENT not in repo.requirements:
         return
-    repo.vfs.rename(backupname, FILENAME, checkambig=True)
+    repo.vfs.rename(backupname, FILENAME)
 
 def clearbackup(repo, backupname):
     if repository.NARROW_REQUIREMENT not in repo.requirements: