Official Unity Space Shooter Tutorial

I am following the space shooter tutorial and I am getting this error error

CS0266: Cannot implicitly convert type UnityEngine.Object' to UnityEngine.GameObject'. An explicit conversion exists (are you missing a cast?)

 using UnityEngine;
 using System.Collections;
 
 [System.Serializable]
 public class Boundary 
 {
     public float xMin, xMax, zMin, zMax;
 }
 
 public class PlayerController : MonoBehaviour 
 {
     public float speed;
     public Boundary boundary;
     public float tilt;
     public GameObject bolt;
     public Transform shotSpawn;
     public float fireRate;
     private float nextFire;
 
 
     void Update() 
     {
                 //allows player to fire weapon and determines a firerate for the next shot fired.
                 if (Input.GetButton ("Fire1") && Time.time > nextFire) 
                 {
                         nextFire = Time.time + fireRate;
                         GameObject clone = Instantiate (bolt, shotSpawn.position, shotSpawn.rotation); // as GameObject; 
                 }
 
     }
 
     void FixedUpdate ()
     {
         //Move player left and right and up and down the screen
         float moveHorizontal = Input.GetAxis ("Horizontal");
         float moveVertical = Input.GetAxis ("Vertical");
 
         Vector3 movement = new Vector3 (moveHorizontal, 0.0f, moveVertical);
         rigidbody.velocity = movement * speed;
 
         //Keeps player from leaving game area by clamping player with bounds.
         rigidbody.position = new Vector3 
         (
             Mathf.Clamp (rigidbody.position.x, boundary.xMin, boundary.xMax),
             0.0f,
             Mathf.Clamp (rigidbody.position.z, boundary.zMin, boundary.zMax)
         );
         //Make player ship tilt when going left or right
         rigidbody.rotation = Quaternion.Euler (0.0f, rigidbody.velocity.x * -tilt);
 
     
     }
 }

Any help with this would be greatly appreciated