Attaching actor to actor in constructor

The code in my parent-actor-constructor:

	UWorld* world = GetWorld();
	if (world != nullptr)
		FActorSpawnParameters spawnParams;
		spawnParams.Owner = this;
		spawnParams.SpawnCollisionHandlingOverride = ESpawnActorCollisionHandlingMethod::AlwaysSpawn;
		AC_BoardSpot* newBS = GetWorld()->SpawnActor<AC_BoardSpot>(AC_BoardSpot::StaticClass(), GetTransform(), spawnParams);
		newBS->AttachToActor(this, FAttachmentTransformRules::KeepRelativeTransform); // <<< problem here

Error in SceneComponent.cpp when I drag the parent into the level:

if (ensureMsgf(AttachParent == nullptr || !AttachParent->AttachChildren.Contains(this), TEXT("SetupAttachment cannot be used once a component has already had AttachTo used to connect it to a parent."))) // UE4Editor-Win64-DebugGame.exe has triggered a breakpoint.

Both actors use a dummy root if that matters:

// Dummy Root.
RootComponent = CreateDefaultSubobject<USceneComponent>(TEXT(ROOT_NAME));

Moving the code to the

virtual void OnConstruction(const FTransform& Transform) override;

did the trick.