diff --git a/src/platforms/stm32/dfucore.c b/src/platforms/stm32/dfucore.c
index f020e61..61cfd04 100644
--- a/src/platforms/stm32/dfucore.c
+++ b/src/platforms/stm32/dfucore.c
@@ -124,12 +124,13 @@ static const char *usb_strings[] = {
 	if_string,
 };
 
+static char upd_if_string[] = UPD_IFACE_STRING;
 static const char *usb_strings_upd[] = {
 	"Black Sphere Technologies",
 	BOARD_IDENT_UPD,
 	serial_no,
 	/* This string is used by ST Microelectronics' DfuSe utility */
-	UPD_IFACE_STRING,
+	upd_if_string,
 };
 
 static uint32_t get_le32(const void *vp)
@@ -355,6 +356,12 @@ static char *get_dev_unique_id(char *s)
 	if (fuse_flash_size == 0x40) /* Handle F103x8 as F103xC! */
 		fuse_flash_size = 0x80;
 	max_address = FLASH_BASE + (fuse_flash_size << 10);
+	/* If bootloader pages are write protected or device is read
+	 * protected, deny bootloader update.
+	 * User can still force updates, at his own risk!
+	 */
+	if (((FLASH_WRPR & 0x03) != 0x03) || (FLASH_OBR & FLASH_OBR_RDPRT_EN))
+		upd_if_string[30] = '0';
 	/* Fetch serial number from chip's unique ID */
 	for(i = 0; i < 8; i++) {
 		s[7-i] = ((unique_id >> (4*i)) & 0xF) + '0';