diff --git a/packages/services/voice-agent/src/plugins/speechmatics_stt.py b/packages/services/voice-agent/src/plugins/speechmatics_stt.py
index edcf9cb..f1b4fea 100644
--- a/packages/services/voice-agent/src/plugins/speechmatics_stt.py
+++ b/packages/services/voice-agent/src/plugins/speechmatics_stt.py
@@ -16,7 +16,7 @@ logger = logging.getLogger(__name__)
 
 # Map Whisper language codes to Speechmatics language codes
 _LANG_MAP = {
-    "zh": "cmn",
+    "zh": "cmn_en",
     "en": "en",
     "ja": "ja",
     "ko": "ko",