Another fix:
Change Tools->Processor->Atmega 328P to Atmega 328P (Old Bootloader). Remind that the Processor option is only available when you select some specific Boards at Tools>Board.
This worked for my Arduino Nano with CH340, using Arduino IDE 1.8.5 under Linux Ubuntu 17.10. Besides, this will probably happen if you use IDE 1.8.9 or newer and you get an old or cloned Nano.