diff --git a/ports/nrf/common-hal/microcontroller/Processor.c b/ports/nrf/common-hal/microcontroller/Processor.c
index 5564c86c54..edff0fa076 100644
--- a/ports/nrf/common-hal/microcontroller/Processor.c
+++ b/ports/nrf/common-hal/microcontroller/Processor.c
@@ -122,7 +122,6 @@ void common_hal_mcu_processor_get_uid(uint8_t raw_id[]) {
     }
 }
 
-extern uint32_t reset_reason_saved;
 mcu_reset_reason_t common_hal_mcu_processor_get_reset_reason(void) {
     mcu_reset_reason_t r = RESET_REASON_UNKNOWN;
     if (reset_reason_saved == 0) {
diff --git a/ports/nrf/common-hal/microcontroller/Processor.h b/ports/nrf/common-hal/microcontroller/Processor.h
index 4049c165fb..1abbe1e4eb 100644
--- a/ports/nrf/common-hal/microcontroller/Processor.h
+++ b/ports/nrf/common-hal/microcontroller/Processor.h
@@ -36,4 +36,6 @@ typedef struct {
     // Stores no state currently.
 } mcu_processor_obj_t;
 
+extern uint32_t reset_reason_saved;
+
 #endif // MICROPY_INCLUDED_NRF_COMMON_HAL_MICROCONTROLLER_PROCESSOR_H