Error on USTRUCT's GENERATED_BODY

Hi,
Sorry if this question was resolved because I read many similars posts but I still can’t resolve my issue (I’m new to Unreal Engine 4).

When I’m declaring my UStruct in the header file of a custom class, the compilation failed on the line GENERATED_BODY() of the UStruct (even with the ~.generated.h file inclued) with the message : “the declaration has no storage class or type specifier”.

When I remove the Ustruct declaration, the compilation works.
Here is my code :

// Fill out your copyright notice in the Description page of Project Settings.

#pragma once

#include "GameFramework/Actor.h"
#include "Room.generated.h"

USTRUCT(BlueprintType)
struct MyStruct {
	GENERATED_BODY() // Here is the error

	UPROPERTY()
	float structVar;
};

UCLASS(Blueprintable, Abstract)
class HACK_N_SLASH_C_API ARoom : public AActor
{
	GENERATED_BODY()

public:	
	// Sets default values for this actor's properties
	ARoom();

	UPROPERTY(EditAnywhere, BlueprintReadWrite)
	float testVar;

	// Called when the game starts or when spawned
	virtual void BeginPlay() override;

	// Called every frame
	virtual void Tick( float DeltaSeconds ) override;
};

I work with Unreal Engine 4.12 and Visual Studio 2015. Nothing changes with many cleans and builds.

How can I declare my Ustruct ?

Thanks ! Visual Studio still indicates an error but the build succeed … I feel dumb for missing it