diff -r 7b0cc86c5d74 -r 6e749d4abf05 mercurial/commandserver.py
--- a/mercurial/commandserver.py	Thu Feb 02 17:20:46 2023 +0100
+++ b/mercurial/commandserver.py	Thu Feb 02 17:20:54 2023 +0100
@@ -332,7 +332,7 @@
             # any kind of interaction must use server channels, but chg may
             # replace channels by fully functional tty files. so nontty is
             # enforced only if cin is a channel.
-            if not util.safehasattr(self.cin, b'fileno'):
+            if not util.safehasattr(self.cin, 'fileno'):
                 ui.setconfig(b'ui', b'nontty', b'true', b'commandserver')
 
         req = dispatch.request(