diff --git a/ports/esp8266/common-hal/microcontroller/Processor.c b/ports/esp8266/common-hal/microcontroller/Processor.c
index 097cc34b58..3602228d03 100644
--- a/ports/esp8266/common-hal/microcontroller/Processor.c
+++ b/ports/esp8266/common-hal/microcontroller/Processor.c
@@ -29,6 +29,7 @@
 #include <math.h>
 
 #include "esp_mphal.h"
+#include "user_interface.h"
 
 
 float common_hal_mcu_processor_get_temperature(void) {