diff -r 1b9be0b26511 -r 23a00bc90a3c mercurial/ui.py
--- a/mercurial/ui.py	Wed Sep 26 21:21:05 2018 +0900
+++ b/mercurial/ui.py	Wed Sep 26 21:24:14 2018 +0900
@@ -231,6 +231,7 @@
             self.fout = src.fout
             self.ferr = src.ferr
             self.fin = src.fin
+            self._finoutredirected = src._finoutredirected
             self.pageractive = src.pageractive
             self._disablepager = src._disablepager
             self._tweaked = src._tweaked
@@ -255,6 +256,7 @@
             self.fout = procutil.stdout
             self.ferr = procutil.stderr
             self.fin = procutil.stdin
+            self._finoutredirected = False
             self.pageractive = False
             self._disablepager = False
             self._tweaked = False