diff --git a/mercurial/util.py b/mercurial/util.py
--- a/mercurial/util.py
+++ b/mercurial/util.py
@@ -2717,7 +2717,7 @@
         pass
 
     try:
-        return socket.getservbyname(port)
+        return socket.getservbyname(pycompat.sysstr(port))
     except socket.error:
         raise Abort(_("no port number associated with service '%s'") % port)