diff --git a/lib_xua/src/core/audiohub/xua_audiohub.xc b/lib_xua/src/core/audiohub/xua_audiohub.xc
index 0a742b39..105e93a1 100755
--- a/lib_xua/src/core/audiohub/xua_audiohub.xc
+++ b/lib_xua/src/core/audiohub/xua_audiohub.xc
@@ -90,7 +90,7 @@ unsigned dsdMode = DSD_MODE_OFF;
 #endif
 
 #pragma unsafe arrays
-static inline unsigned DoSampleTransfer(chanend c_out, const int readBuffNo, const unsigned underflowWord)
+static inline unsigned DoSampleTransfer(chanend ?c_out, const int readBuffNo, const unsigned underflowWord)
 {
     if(XUA_USB_EN)
     {