diff --git a/src/stm32/gpio.h b/src/stm32/gpio.h
index 96105e9b..6a5f910c 100644
--- a/src/stm32/gpio.h
+++ b/src/stm32/gpio.h
@@ -24,7 +24,7 @@ uint8_t gpio_in_read(struct gpio_in g);
 struct gpio_pwm {
   void *reg;
 };
-struct gpio_pwm gpio_pwm_setup(uint8_t pin, uint32_t cycle_time, uint8_t val);
+struct gpio_pwm gpio_pwm_setup(uint8_t pin, uint32_t cycle_time, uint32_t val);
 void gpio_pwm_write(struct gpio_pwm g, uint32_t val);
 
 struct gpio_adc {
diff --git a/src/stm32/hard_pwm.c b/src/stm32/hard_pwm.c
index 09a29ed5..d9be268e 100644
--- a/src/stm32/hard_pwm.c
+++ b/src/stm32/hard_pwm.c
@@ -11,7 +11,7 @@
 #include "internal.h" // GPIO
 #include "sched.h" // sched_shutdown
 
-#define MAX_PWM 255
+#define MAX_PWM (256 + 1)
 DECL_CONSTANT("PWM_MAX", MAX_PWM);
 
 struct gpio_pwm_info {
@@ -275,7 +275,8 @@ static const struct gpio_pwm_info pwm_regs[] = {
 };
 
 struct gpio_pwm
-gpio_pwm_setup(uint8_t pin, uint32_t cycle_time, uint8_t val){
+gpio_pwm_setup(uint8_t pin, uint32_t cycle_time, uint32_t val)
+{
     // Find pin in pwm_regs table
     const struct gpio_pwm_info* p = pwm_regs;
     for (;; p++) {