diff --git a/mercurial/commandserver.py b/mercurial/commandserver.py
--- a/mercurial/commandserver.py
+++ b/mercurial/commandserver.py
@@ -55,7 +55,7 @@ class channeledoutput(object):
         self.out.flush()
 
     def __getattr__(self, attr):
-        if attr in ('isatty', 'fileno'):
+        if attr in ('isatty', 'fileno', 'tell', 'seek'):
             raise AttributeError(attr)
         return getattr(self.out, attr)
 
@@ -139,7 +139,7 @@ class channeledinput(object):
         return l
 
     def __getattr__(self, attr):
-        if attr in ('isatty', 'fileno'):
+        if attr in ('isatty', 'fileno', 'tell', 'seek'):
             raise AttributeError(attr)
         return getattr(self.in_, attr)