Set is not working with Variables defined in extended configurations

[FrankSoldner]

The following example is not working as described. Hence with the 'ArtifactName' it is working.

Project {

ExecutableConfig DebugBase {
    Files "**/*.cpp"
    Files "**/*.c"

...

    ArtifactName "ulp_$(FIRMWARE_MODEL_NAME)_z4App_debug.elf"

    Set FIRMWARE_BIN_FILE_NAME, value: "$(ArtifactNameBase)-v$(FIRMWARE_VERSION_MAJOR).$(FIRMWARE_VERSION_MINOR).$(FIRMWARE_VERSION_PATCH).bin"
    Set OTA_BASE_NAME, value: "AudiULP-$(FIRMWARE_MODEL_NAME)-OTA-FW-Gateway"

... }

ExecutableConfig DebugMLB, extends: DebugBase {

    Set FIRMWARE_VERSION_MAJOR, value: "2"
    Set FIRMWARE_MODEL_NAME, value: "C7"    

    DefaultToolchain Diab {
        Compiler CPP {
            Define USE_MLB
        }
    }
}

ExecutableConfig DebugMLBevo, extends: DebugBase {

    Set FIRMWARE_VERSION_MAJOR, value: "3"
    Set FIRMWARE_MODEL_NAME, value: "Q7"

    DefaultToolchain Diab {
        Compiler CPP {
            Define USE_MLBevo
        }
    }
}

}