Help with Instantiating

Alright people, when all else fails go to the Answers. This should be easy for anybody more experienced than me. I sort of understand what the problem is but I can’t think of what I have to do to fix it. projectilePrefab is a GameObject and changing it to an object doesn’t resolve the issue. The error is as follows:

Assets/First-Third Person Shooter/Resources/Scripts/Weapon/Gun.cs(273,28): error CS0266: Cannot implicitly convert type UnityEngine.Object' to UnityEngine.GameObject’. An explicit conversion exists (are you missing a cast?)

		GameObject projectile = GameObject.Instantiate(projectilePrefab, startPosition, Quaternion.identity);

GameObject projectile = GameObject.Instantiate(projectilePrefab, startPosition, Quaternion.identity) as GameObject;