Plugin Character Base Class Load in GameMode as DefaultPawn

I made a character base class in a plugin and used it a base class for blueprint. I want to load it in gamemode as default pawn, but the constructor seems to be to early.

    //static ConstructorHelpers::FClassFinder<APawn> PlayerPawnObject(TEXT("/Game/CustomeCharacter"));
    //if (PlayerPawnObject.Class != NULL)
    //    DefaultPawnClass = PlayerPawnObject.Class;

this only works if i comment it in, when the engine is running and i press compile script.
How i can load it later?

Thank you!