diff --git a/rtcllm/stt.py b/rtcllm/stt.py
index 0c73c7b..d885076 100644
--- a/rtcllm/stt.py
+++ b/rtcllm/stt.py
@@ -34,6 +34,8 @@ opts = {
 }
 
 async def asr(a_file):
+	if not a_file:
+		return
 	oc  = OAuthClient(DictObject(**opts))
 	r = await oc('http://open-computing.cn', 'asr', {'audio_file':f})
 	print(f'{r=}')