diff --git a/drivers/net/ethernet/cadence/macb.h b/drivers/net/ethernet/cadence/macb.h
index 31dc080f2437..ff85619a9732 100644
--- a/drivers/net/ethernet/cadence/macb.h
+++ b/drivers/net/ethernet/cadence/macb.h
@@ -351,7 +351,7 @@
 
 /* Bitfields in MID */
 #define MACB_IDNUM_OFFSET			16
-#define MACB_IDNUM_SIZE				16
+#define MACB_IDNUM_SIZE				12
 #define MACB_REV_OFFSET				0
 #define MACB_REV_SIZE				16