diff --git a/target/linux/ifxmips/files/arch/mips/include/asm/mach-ifxmips/ifxmips.h b/target/linux/ifxmips/files/arch/mips/include/asm/mach-ifxmips/ifxmips.h
index c8cf0aef5..1076dc463 100644
--- a/target/linux/ifxmips/files/arch/mips/include/asm/mach-ifxmips/ifxmips.h
+++ b/target/linux/ifxmips/files/arch/mips/include/asm/mach-ifxmips/ifxmips.h
@@ -223,7 +223,7 @@
 #define MDIO_ACC_READ			0x40000000
 #define MDIO_ACC_ADDR_MASK		0x1f
 #define MDIO_ACC_ADDR_OFFSET		0x15
-#define MDIO_ACC_REG_MASK		0xff
+#define MDIO_ACC_REG_MASK		0x1f
 #define MDIO_ACC_REG_OFFSET		0x10
 #define MDIO_ACC_VAL_MASK		0xffff