ISO C++ forbids forward references

When I build the linux server . it show me a error

this is what the code is

UENUM(BlueprintType)
enum EPropStateType
{
	PROPSTATE_Deactivated UMETA(DisplayName = "Deactivated"),
	PROPSTATE_Activated	  UMETA(DisplayName = "Activated"),
};

DECLARE_DYNAMIC_MULTICAST_DELEGATE_OneParam(FPropStateChangedDelegate, EPropStateType, PropCurrentState);

the problem happen in EPropStateType