diff --git a/bootloader/F4/Src/main.c b/bootloader/F4/Src/main.c
index abda4430..df436d38 100644
--- a/bootloader/F4/Src/main.c
+++ b/bootloader/F4/Src/main.c
@@ -79,7 +79,7 @@ static uint8_t CMD_SIGNATURE[7] = {'B','T','L','D','C','M','D'};
 
 /* Command: <Send next data pack> */
 static uint8_t CMD_DATA_RECEIVED[8] = {'B','T','L','D','C','M','D',2};
-uint8_t new_data_is_received = 0;
+volatile uint8_t new_data_is_received = 0;
 static uint8_t pageData[SECTOR_SIZE];
 typedef void (*funct_ptr)(void);
 
diff --git a/bootloader/F4/Src/usbd_custom_hid_if.c b/bootloader/F4/Src/usbd_custom_hid_if.c
index e18a0d42..ceca737a 100644
--- a/bootloader/F4/Src/usbd_custom_hid_if.c
+++ b/bootloader/F4/Src/usbd_custom_hid_if.c
@@ -61,7 +61,7 @@
 /* USER CODE BEGIN PV */
 /* Private variables ---------------------------------------------------------*/
 extern uint8_t USB_RX_Buffer[CUSTOM_HID_EPOUT_SIZE];
-extern uint8_t new_data_is_received;
+extern volatile uint8_t new_data_is_received;
 /* USER CODE END PV */
 
 /** @addtogroup STM32_USB_OTG_DEVICE_LIBRARY