AVR assembler code for ATmega328PB

I am working on a project where I want to mix C-code and some Assembler code. This works fine in Microchip studio, and after a few days of configuring Platform.IO I did manage to have it working for an ATmega328P.
Now I am trying to get it to work with an ATmega328PB and the compilation fails with this message :

Known MCU names:

Assembler messages:
Fatal error: unknown MCU: atmega328pb

This error is caused by the assembly file only , but it compiles correctly for an ATmega328P
Who can help me out ?

my platformio.ini file looks like this :
platform = atmelavr
upload_protocol = atmelice_isp
upload_flags = -e
board = ATmega328PB
board_build.mcu = atmega328pb
board_build.f_cpu = 16000000UL
board_upload.require_upload_port = no
platform_packages = toolchain-atmelavr@>=1.70300.0 ; use GCC AVR 7.3.0+

If PlatformIO passes the wrong -mmcu flag for the assembler, please file a bug in Issues · platformio/platform-atmelavr · GitHub.