diff -r 15c998528c36 -r 21fa3d3688f3 mercurial/simplemerge.py
--- a/mercurial/simplemerge.py	Tue Mar 07 12:52:00 2017 -0800
+++ b/mercurial/simplemerge.py	Thu Mar 02 03:52:36 2017 +0100
@@ -437,7 +437,7 @@
 
     local = os.path.realpath(local)
     if not opts.get('print'):
-        opener = scmutil.opener(os.path.dirname(local))
+        opener = scmutil.vfs(os.path.dirname(local))
         out = opener(os.path.basename(local), "w", atomictemp=True)
     else:
         out = ui.fout