diff --git a/module_usb_audio/usb_buffer/decouple.xc b/module_usb_audio/usb_buffer/decouple.xc
index a7048323..e05101d3 100644
--- a/module_usb_audio/usb_buffer/decouple.xc
+++ b/module_usb_audio/usb_buffer/decouple.xc
@@ -25,7 +25,7 @@
 #define MAX_USB_AUD_PACKET_SIZE 1028
 
 #define OUT_BUFFER_PREFILL (MAX(NUM_USB_CHAN_OUT_FS*FS_PACKET_SIZE*3+4,NUM_USB_CHAN_OUT*HS_PACKET_SIZE*4+4)*1)
-#define IN_BUFFER_PREFILL (MAX(FS_PACKET_SIZE*2+4,1*HS_PACKET_SIZE*4+4)*2)
+#define IN_BUFFER_PREFILL (MAX(FS_PACKET_SIZE*2+4, NUM_USB_CHAN_IN*HS_PACKET_SIZE*4+4)*2)
 
 /* Volume and mute tables */
 #ifndef OUT_VOLUME_IN_MIXER