diff --git a/lib/server.js b/lib/server.js
index 37c4c99..e05c5ce 100644
--- a/lib/server.js
+++ b/lib/server.js
@@ -47,7 +47,10 @@ function Server(options, isSecure, onListening) {
           else {
             xml = Serializer.serializeMethodResponse(value)
           }
-          response.writeHead(200, {'Content-Type': 'text/xml'})
+          response.writeHead(200, {
+            'Content-Type': 'text/xml',
+            'Content-Length': Buffer.byteLength(xml, 'utf8')
+          })
           response.end(xml)
         })
       }