diff --git a/lib/synth-audio.js b/lib/synth-audio.js
index f7f4a96..894e6df 100644
--- a/lib/synth-audio.js
+++ b/lib/synth-audio.js
@@ -412,6 +412,7 @@ const synthMicrosoft = async(logger, {
       params += `,language=${language}`;
       params += ',vendor=microsoft';
       params += `,voice=${voice}`;
+      params += ',write_cache_file=1';
       if (region) params += `,region=${region}`;
       if (custom_tts_endpoint) params += `,endpointId=${custom_tts_endpoint}`;
       if (process.env.JAMBONES_HTTP_PROXY_IP) params += `,http_proxy_ip=${process.env.JAMBONES_HTTP_PROXY_IP}`;