diff -r 1b9be0b26511 -r 23a00bc90a3c mercurial/wireprotoserver.py
--- a/mercurial/wireprotoserver.py	Wed Sep 26 21:21:05 2018 +0900
+++ b/mercurial/wireprotoserver.py	Wed Sep 26 21:24:14 2018 +0900
@@ -785,6 +785,8 @@
         self._ui = ui
         self._repo = repo
         self._fin, self._fout = procutil.protectstdio(ui.fin, ui.fout)
+        # TODO: manage the redirection flag internally by ui
+        ui._finoutredirected = (self._fin, self._fout) != (ui.fin, ui.fout)
 
         # Log write I/O to stdout and stderr if configured.
         if logfh: