diff --git a/hg b/hg
--- a/hg
+++ b/hg
@@ -10,6 +10,11 @@
 import os
 import sys
 
+if os.environ.get('HGUNICODEPEDANTRY', False):
+    reload(sys)
+    sys.setdefaultencoding("undefined")
+
+
 libdir = '@LIBDIR@'
 
 if libdir != '@' 'LIBDIR' '@':