Problem with classes in different files

[Bingocat4]

I decided to try putting classes into different files to see how that worked. It didn't work. Whenever I have a function in a class that needs a different class it gives an error. Here is my code:

#pragma once
#include <allegro5\allegro.h>
#include <allegro5\allegro_image.h>
#include <vector>
#include "Bullet.h"

using namespace std;

class Player {
private:
	int x, y, width, height;
	int keys[3] = { false, false, false };
	ALLEGRO_BITMAP *image;
	bool shot;

public:
	Player();
	void Update(vector<Bullet> &bullets, ALLEGRO_BITMAP *bulletImage);
	void Draw();
};

I get this error:

error C2065: 'Bullet': undeclared identifier
error C2923: 'std::vector': 'Bullet' is not a valid template type argument for parameter '_Ty'

[Bingocat4]

Never mind. I found my answer here:

http://stackoverflow.com/questions/4964482/how-to-create-two-classes-in-c-which-use-each-other-as-data