diff --git a/lib/usb_dfu.c b/lib/usb_dfu.c
index 7ede937..62f707c 100644
--- a/lib/usb_dfu.c
+++ b/lib/usb_dfu.c
@@ -328,11 +328,11 @@ void usb_dfu_setup(void)
 	for (uint8_t i = 0; i < LENGTH(usb_serial) - 1; i++) { // write the serial
 		uint32_t id; // current ID part
 		if (i < 8) {
-			id = DESIG_UNIQUE_ID0;
+			id = DESIG_UNIQUE_ID2;
 		} else if (i < 16) {
 			id = DESIG_UNIQUE_ID1;
 		} else {
-			id = DESIG_UNIQUE_ID2;
+			id = (DESIG_UNIQUE_ID0 << 16) + (DESIG_UNIQUE_ID0 >> 16);
 		}
 		// transform into character
 		char c = (id >> ((7 - (i % 8)) * 4)) & 0x0f; // get nibble