static int stm32x_mass_erase(struct flash_bank *bank)
 {
        int retval;
+       uint32_t flash_mer;
        struct target *target = bank->target;
        struct stm32x_flash_bank *stm32x_info = NULL;
 
 
        /* mass erase flash memory */
        if (stm32x_info->has_large_mem)
-               retval = target_write_u32(target, stm32x_get_flash_reg(bank, STM32_FLASH_CR), FLASH_MER | FLASH_MER1);
+               flash_mer = FLASH_MER | FLASH_MER1;
        else
-               retval = target_write_u32(target, stm32x_get_flash_reg(bank, STM32_FLASH_CR), FLASH_MER);
+               flash_mer = FLASH_MER;
+       retval = target_write_u32(target, stm32x_get_flash_reg(bank, STM32_FLASH_CR), flash_mer);
        if (retval != ERROR_OK)
                return retval;
        retval = target_write_u32(target, stm32x_get_flash_reg(bank, STM32_FLASH_CR),
-               FLASH_MER | FLASH_STRT);
+               flash_mer | FLASH_STRT);
        if (retval != ERROR_OK)
                return retval;