diff --git a/mercurial/commandserver.py b/mercurial/commandserver.py
--- a/mercurial/commandserver.py
+++ b/mercurial/commandserver.py
@@ -73,8 +73,8 @@ class channeledinput(object):
             s = self._read(size, self.channel)
             buf = s
             while s:
+                s = self._read(size, self.channel)
                 buf += s
-                s = self._read(size, self.channel)
 
             return buf
         else:
@@ -104,8 +104,8 @@ class channeledinput(object):
             # keep asking for more until there's either no more or
             # we got a full line
             while s and s[-1] != '\n':
+                s = self._read(size, 'L')
                 buf += s
-                s = self._read(size, 'L')
 
             return buf
         else: