diff --git a/lib/synth-audio.js b/lib/synth-audio.js
index 4d25abe..f44723d 100644
--- a/lib/synth-audio.js
+++ b/lib/synth-audio.js
@@ -353,7 +353,8 @@ async function _synthMicrosoftByHttp(logger, {
   try {
     const post = bent('POST', 'buffer', {
       'X-Microsoft-OutputFormat': 'audio-16khz-128kbitrate-mono-mp3',
-      'Content-Type': 'application/ssml+xml'
+      'Content-Type': 'application/ssml+xml',
+      'User-Agent': 'Jambonz'
     });
     const mp3 = await post(custom_tts_endpoint_url, content);
     return mp3;