diff --git a/lib/usb_cdcacm.c b/lib/usb_cdcacm.c
index 95c1874..8c6f707 100644
--- a/lib/usb_cdcacm.c
+++ b/lib/usb_cdcacm.c
@@ -444,7 +444,7 @@ static void usb_cdcacm_set_config(usbd_device *usbd_dev, uint16_t wValue)
 
 void usb_cdcacm_setup(void)
 {
-	snprintf(usb_serial, LENGTH(usb_serial), "%08x%08x%08x", DESIG_UNIQUE_ID0, DESIG_UNIQUE_ID1, DESIG_UNIQUE_ID2); // set actual device ID as serial
+	snprintf(usb_serial, LENGTH(usb_serial), "%08x%08x%04x%04x", DESIG_UNIQUE_ID2, DESIG_UNIQUE_ID1, DESIG_UNIQUE_ID0 & 0xffff, DESIG_UNIQUE_ID0 >> 16); // set actual device ID as serial
 
 	// initialize USB
 	rcc_periph_reset_pulse(RST_USB); // reset USB peripheral