diff --git a/lib/routes/api/accounts.js b/lib/routes/api/accounts.js
index d72c8ab..397c31b 100644
--- a/lib/routes/api/accounts.js
+++ b/lib/routes/api/accounts.js
@@ -105,6 +105,7 @@ async function validateCreateCall(logger, sid, req) {
         call_hook: application.call_hook,
         call_status_hook: application.call_status_hook,
         speech_synthesis_vendor: application.speech_synthesis_vendor,
+        speech_synthesis_language: application.speech_synthesis_language,
         speech_synthesis_voice: application.speech_synthesis_voice,
         speech_recognizer_vendor: application.speech_recognizer_vendor,
         speech_recognizer_language: application.speech_recognizer_language
@@ -122,6 +123,7 @@ async function validateCreateCall(logger, sid, req) {
     Object.assign(obj, {
       speech_synthesis_vendor: 'google',
       speech_synthesis_voice: 'en-US-Wavenet-C',
+      speech_synthesis_language: 'en-US',
       speech_recognizer_vendor: 'google',
       speech_recognizer_language: 'en-US'
     });