diff --git a/src/jtag/drivers/cmsis_dap_usb_bulk.c b/src/jtag/drivers/cmsis_dap_usb_bulk.c
index 29104d3a5..09efa3c63 100644
--- a/src/jtag/drivers/cmsis_dap_usb_bulk.c
+++ b/src/jtag/drivers/cmsis_dap_usb_bulk.c
@@ -414,7 +414,7 @@ static int cmsis_dap_usb_write(struct cmsis_dap *dap, int txlen, int timeout_ms)
 	int err;
 	int tail = 0;
 
-	if ((txlen < dap->packet_buffer_size) && !(txlen % dap->packet_size)) {
+	if ((txlen < (int)dap->packet_buffer_size) && !(txlen % dap->packet_size)) {
 		tail = 1;
 	}