diff --git a/sendgrid/transport/web.py b/sendgrid/transport/web.py
index 1d543a30d..d2d75cb3a 100644
--- a/sendgrid/transport/web.py
+++ b/sendgrid/transport/web.py
@@ -86,6 +86,8 @@ def send(self, message):
         for key in optional_params:
             if optional_params[key]:
                 data[key] = optional_params[key]
+                if isinstance(data[key], unicode):
+                    data[key] = data[key].encode('utf-8')
 
         data = urllib.urlencode(data, 1)
         req = urllib2.Request(url, data)