diff -r 9e8fcd2e78c1 -r a9f56e4501c1 mercurial/ui.py
--- a/mercurial/ui.py	Tue Sep 25 08:53:20 2018 -0700
+++ b/mercurial/ui.py	Wed Sep 26 08:46:56 2018 -0700
@@ -234,6 +234,7 @@
             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
@@ -258,6 +259,7 @@
             self.fout = procutil.stdout
             self.ferr = procutil.stderr
             self.fin = procutil.stdin
+            self._finoutredirected = False
             self.pageractive = False
             self._disablepager = False
             self._tweaked = False