const float not allowed in USTRUCT ?

not sure if it’s a bug or a normal thing, but this code won’t compile while removing the const keyword will compile fine.
any explanation ?

USTRUCT()
struct FDamageFeedbackItem
{


	FDamageFeedbackItem()
	{
		RemainingTime = 0.f;
		MinVisibility = 0.f;
		Visibility = 0.f;
		ImgWidget = NULL;
	}

	GENERATED_USTRUCT_BODY()
public:
	const float FadeOutTime = 0.2f;
	UPROPERTY()
		float RemainingTime;
	UPROPERTY()
		float MinVisibility;
	UPROPERTY()
		float Visibility;
	UPROPERTY()
	UImage* ImgWidget;
};