How to destroy all gameobjects with a tag (loop doesn't work)

I would like to destroy all gameobjects with a tag instantly, but when I use a loop:

GameObject[] enemies = GameObject.FindGameObjectsWithTag("Enemy");
foreach(GameObject enemy in enemies)
  GameObject.Destroy(enemy);

Assets/scripts/moveboxes.cs(186,33): error CS1503: Argument #1' cannot convert UnityEngine.GameObject’ expression to type `UnityEngine.Object’

Thanks

This script tested fine for me in unity 5.1.2f1.

public class Kill_Enemies : MonoBehaviour {
	void Start () 
	{
		GameObject[] enemies = GameObject.FindGameObjectsWithTag("Enemy");
		foreach(GameObject enemy in enemies)
		GameObject.Destroy(enemy);
	}
}