diff --git a/xtts/bridge.js b/xtts/bridge.js
index d2783f5..023925c 100644
--- a/xtts/bridge.js
+++ b/xtts/bridge.js
@@ -214,10 +214,12 @@ async function _runTTSRequest(payload) {
  */
 function streamXTTSAsPCM(text, language, speakerWav, onPcmChunk) {
   return new Promise((resolve, reject) => {
+    // Wichtig: speaker_wav MUSS als Query-Key dabei sein (Pydantic required) —
+    // auch bei default-voice mit leerem Wert. Sonst gibt's HTTP 422.
     const qs = new URLSearchParams();
     qs.set("text", text);
     qs.set("language", language || "de");
-    if (speakerWav) qs.set("speaker_wav", speakerWav);
+    qs.set("speaker_wav", speakerWav || "");
     qs.set("stream_chunk_size", "40");
 
     const url = new URL(XTTS_API_URL);