diff --git a/lib_xua/src/core/buffer/ep/ep_buffer.xc b/lib_xua/src/core/buffer/ep/ep_buffer.xc
index fa43faa7..2aa2218e 100644
--- a/lib_xua/src/core/buffer/ep/ep_buffer.xc
+++ b/lib_xua/src/core/buffer/ep/ep_buffer.xc
@@ -247,7 +247,7 @@ void XUA_Buffer_Ep(register chanend c_aud_out,
 #if (NUM_USB_CHAN_IN > 0)
     unsigned bufferIn = 1;
 #endif
-    unsigned sofCount = 0;
+    int sofCount = 0;
     int pllUpdate = 0;
 
     unsigned mod_from_last_time = 0;