diff --git a/include/libopencm3/swm050/timer.h b/include/libopencm3/swm050/timer.h
index 8748b3a1..f3535748 100644
--- a/include/libopencm3/swm050/timer.h
+++ b/include/libopencm3/swm050/timer.h
@@ -93,12 +93,6 @@ enum timer_pwm_period {
 /** Timer Clock Divider Mask */
 #define TIMER_DIV_MASK			(0x3F << 16)
 
-/** Timer Operation Mode Mask */
-#define TIMER_OPER_MODE_MASK		(0x3 << 4)
-
-/** Timer Output Mode Mask */
-#define TIMER_OUTP_MODE_MASK		(0x3 << 12)
-
 /** @defgroup timer_registers Timer Registers
 @{*/
 /** Timer control register */
@@ -135,6 +129,12 @@ enum timer_pwm_period {
 #define TIMER_CTRL_TMOD		(1 << 16)
 /** Loop mode selection */
 #define TIMER_CTRL_LMOD		(1 << 28)
+/** Timer Output Mode Mask */
+#define TIMER_CTRL_OUTMOD_MASK	0x3
+#define TIMER_CTRL_OUTMOD_SHIFT	12
+/** Timer Operation Mode Mask */
+#define TIMER_CTRL_WMOD_MASK	0x3
+#define TIMER_CTRL_WMOD_SHIFT	4
 /** Interrupt mask */
 #define TIMER_INTCTL_INTMSK	(1 << 1)
 /** Interrupt enable */
diff --git a/lib/swm050/timer.c b/lib/swm050/timer.c
index 8ae53a19..7c178558 100644
--- a/lib/swm050/timer.c
+++ b/lib/swm050/timer.c
@@ -233,8 +233,8 @@ void timer_clock_enable(uint32_t timer, bool en)
  */
 void timer_operation_mode(uint32_t timer, enum timer_operation_modes mode)
 {
-	mode = (mode << 4);
-	TIMER_CTRL(timer) = (~TIMER_OPER_MODE_MASK & TIMER_CTRL(timer)) | mode;
+	uint32_t reg = TIMER_CTRL(timer) & ~(TIMER_CTRL_OUTMOD_MASK << TIMER_CTRL_OUTMOD_SHIFT);
+	TIMER_CTRL(timer) = reg | (mode << TIMER_CTRL_OUTMOD_SHIFT);
 }
 
 /**
@@ -251,8 +251,8 @@ void timer_operation_mode(uint32_t timer, enum timer_operation_modes mode)
  */
 void timer_output_mode(uint32_t timer, enum timer_output_modes mode)
 {
-	mode = (mode << 12);
-	TIMER_CTRL(timer) = (~TIMER_OUTP_MODE_MASK & TIMER_CTRL(timer)) | mode;
+	uint32_t reg = TIMER_CTRL(timer) & ~(TIMER_CTRL_WMOD_MASK << TIMER_CTRL_WMOD_SHIFT);
+	TIMER_CTRL(timer) = reg | (mode << TIMER_CTRL_WMOD_SHIFT);
 }
 
 /**