diff -r 5be286db5fb5 -r d4a2e0d5d042 mercurial/server.py
--- a/mercurial/server.py	Sat Mar 24 13:38:04 2018 +0900
+++ b/mercurial/server.py	Sat Mar 24 15:09:33 2018 +0900
@@ -22,6 +22,10 @@
     util,
 )
 
+from .utils import (
+    procutil,
+)
+
 def runservice(opts, parentfn=None, initfn=None, runfn=None, logfile=None,
                runargs=None, appendpid=False):
     '''Run a command as a service.'''
@@ -87,8 +91,8 @@
                 raise error.Abort(_('invalid value for --daemon-postexec: %s')
                                   % inst)
         util.hidewindow()
-        util.stdout.flush()
-        util.stderr.flush()
+        procutil.stdout.flush()
+        procutil.stderr.flush()
 
         nullfd = os.open(os.devnull, os.O_RDWR)
         logfilefd = nullfd