diff --git a/ports/nrf/bluetooth/ble_drv.c b/ports/nrf/bluetooth/ble_drv.c
index 63d67a7f4a..7dbb315826 100644
--- a/ports/nrf/bluetooth/ble_drv.c
+++ b/ports/nrf/bluetooth/ble_drv.c
@@ -43,7 +43,7 @@
 nrf_nvic_state_t nrf_nvic_state = { 0 };
 
 // Flag indicating progress of internal flash operation.
-sd_flash_operation_status_t sd_flash_operation_status;
+volatile sd_flash_operation_status_t sd_flash_operation_status;
 
 __attribute__((aligned(4)))
 static uint8_t m_ble_evt_buf[sizeof(ble_evt_t) + (BLE_GATT_ATT_MTU_DEFAULT)];
diff --git a/ports/nrf/bluetooth/ble_drv.h b/ports/nrf/bluetooth/ble_drv.h
index 7716cab8be..91990da6df 100644
--- a/ports/nrf/bluetooth/ble_drv.h
+++ b/ports/nrf/bluetooth/ble_drv.h
@@ -59,7 +59,7 @@ typedef enum {
 } sd_flash_operation_status_t;
 
 // Flag indicating progress of internal flash operation.
-extern sd_flash_operation_status_t sd_flash_operation_status;
+extern volatile sd_flash_operation_status_t sd_flash_operation_status;
 
 typedef struct ble_drv_evt_handler_entry {
     struct ble_drv_evt_handler_entry *next;