diff --git a/ports/esp32/machine_pwm.c b/ports/esp32/machine_pwm.c
index a51b7eb490a2c..3eb1d42b649c9 100755
--- a/ports/esp32/machine_pwm.c
+++ b/ports/esp32/machine_pwm.c
@@ -52,7 +52,7 @@ to view __FUNCTION__, __LINE__, __FILE__ in exception
 // 10-bit user interface resolution compatible with esp8266 PWM.duty()
 #define UI_RES_10_BIT (10)
 // Maximum duty value on 10-bit resolution
-#define UI10_DUTY ((1UL << UI_RES_10_BIT) - 1)
+#define UI10_DUTY ((1U << UI_RES_10_BIT) - 1)
 
 // 16-bit user interface resolution used in PWM.duty_u16()
 #define UI_RES_16_BIT (16)