diff --git a/include/libopencm3/sam3x/pwm.h b/include/libopencm3/sam3x/pwm.h
index 181b8091..445ff2bd 100644
--- a/include/libopencm3/sam3x/pwm.h
+++ b/include/libopencm3/sam3x/pwm.h
@@ -78,22 +78,22 @@
 #define PWM_DT(x)			MMIO32(PWM_BASE + 0x0218 + 0x20*(x))
 #define PWM_DTUPD(x)			MMIO32(PWM_BASE + 0x021C + 0x20*(x))
 
-static inline pwm_set_period(int ch, u32 period)
+static inline void pwm_set_period(int ch, u32 period)
 {
 	PWM_CPRD(ch) = period;
 }
 
-static inline pwm_set_duty(int ch, u32 duty)
+static inline void pwm_set_duty(int ch, u32 duty)
 {
 	PWM_CDTY(ch) = duty;
 }
 
-static inline pwm_enable(int ch)
+static inline void pwm_enable(int ch)
 {
 	PWM_ENA = 1 << ch;
 }
 
-static inline pwm_disable(int ch)
+static inline void pwm_disable(int ch)
 {
 	PWM_DIS = 1 << ch;
 }