diff --git a/sip/asterisk.py b/sip/asterisk.py
index 84b041a3..b9c6f7aa 100644
--- a/sip/asterisk.py
+++ b/sip/asterisk.py
@@ -86,9 +86,9 @@ class Sms(object):
             f.write(dst)
         with open(path + 'body', 'w') as f:
             if body_type=='str':
-                f.write(body)
-            elif body_type=='base64':
                 f.write(base64.encodestring(body).strip())
+            elif body_type=='base64':
+                f.write(body)