diff --git a/contrib/hgperf b/contrib/hgperf
--- a/contrib/hgperf
+++ b/contrib/hgperf
@@ -94,7 +94,4 @@ def runcommand(lui, repo, cmd, fullargs,
 
 dispatch.runcommand = runcommand
 
-for fp in (sys.stdin, sys.stdout, sys.stderr):
-    util.setbinary(fp)
-
 dispatch.run()
diff --git a/hg b/hg
--- a/hg
+++ b/hg
@@ -37,11 +37,5 @@ except ImportError:
     sys.stderr.write("(check your install and PYTHONPATH)\n")
     sys.exit(-1)
 
-from mercurial import (
-    dispatch,
-    util,
-)
-for fp in (sys.stdin, sys.stdout, sys.stderr):
-    util.setbinary(fp)
-
+from mercurial import dispatch
 dispatch.run()
diff --git a/mercurial/dispatch.py b/mercurial/dispatch.py
--- a/mercurial/dispatch.py
+++ b/mercurial/dispatch.py
@@ -75,6 +75,7 @@ class request(object):
 
 def run():
     "run the command in sys.argv"
+    _initstdio()
     req = request(pycompat.sysargv[1:])
     err = None
     try:
@@ -95,6 +96,10 @@ def run():
         req.ui.ferr.flush()
     sys.exit(status & 255)
 
+def _initstdio():
+    for fp in (sys.stdin, sys.stdout, sys.stderr):
+        util.setbinary(fp)
+
 def _getsimilar(symbols, value):
     sim = lambda x: difflib.SequenceMatcher(None, value, x).ratio()
     # The cutoff for similarity here is pretty arbitrary. It should