diff --git a/sys/mips/atheros/ar933x_uart.h b/sys/mips/atheros/ar933x_uart.h
index 992b152e055..5062ad044bc 100644
--- a/sys/mips/atheros/ar933x_uart.h
+++ b/sys/mips/atheros/ar933x_uart.h
@@ -68,10 +68,13 @@
 #define	AR933X_UART_CS_TX_BUSY		(1 << 14)
 #define	AR933X_UART_CS_RX_BUSY		(1 << 15)
 
-#define	AR933X_UART_CLOCK_STEP_M	0xffff
-#define	AR933X_UART_CLOCK_SCALE_M	0xfff
+#define	AR933X_UART_CLOCK_SCALE_M	0xff
 #define	AR933X_UART_CLOCK_SCALE_S	16
 #define	AR933X_UART_CLOCK_STEP_M	0xffff
+#define	AR933X_UART_CLOCK_STEP_S	0
+
+#define	AR933X_UART_MAX_SCALE		0xff
+#define	AR933X_UART_MAX_STEP		0xffff
 
 #define	AR933X_UART_INT_RX_VALID	(1 << 0)
 #define	AR933X_UART_INT_TX_READY	(1 << 1)