diff --git a/lib/py/cli.py b/lib/py/cli.py
index 94cc2f947..df96729e2 100755
--- a/lib/py/cli.py
+++ b/lib/py/cli.py
@@ -16,7 +16,7 @@ def inf(opts):
 
 def outf(opts):
     if opts['out']:
-        return open(opts['out'], 'w+')
+        return open(opts['out'], 'wb+')
     else:
         return sys.stdout