diff --git a/usb/iso.c b/usb/iso.c
index b83f6b2..6d5ec51 100644
--- a/usb/iso.c
+++ b/usb/iso.c
@@ -3,6 +3,7 @@
 #include <string.h>
 
 void print_xfer(struct libusb_transfer *xfer);
+void iso_callback(void *);
 
 void callback(struct libusb_transfer *xfer) {
 	//printf("Callback!\n");