Missilerotation problem with homing missile

Why my missile rotates 90 degrees to z axis when it starts to follow "enemy" tagged object? Here is the code. Can someone help me to get missile stay rightway. using UnityEngine; using System.Collections;

 public class MoveHMissileScript : MonoBehaviour {
 
     public float speed = 10.0f;
     public float turnspeed = 5.0f;
 
 
 
     private Vector3 Range = new Vector3(0,0,0);
     private GameObject closest;
     
 
 
     void Update ()
         
     {
 
         GameObject[] targets = GameObject.FindGameObjectsWithTag("Enemy");
 
         float closestDist = Mathf.Infinity;
 
         foreach(GameObject Target in targets)    
         {
             
             float dist = (transform.position - Target.transform.position).sqrMagnitude;
 
             if(dist < closestDist)
                 
             {
                 closestDist = dist;
                 
                 closest = Target;            
             }
             
         }
         
 
         
         transform.rotation = Quaternion.Slerp(transform.rotation, Quaternion.LookRotation(closest.transform.position-transform.position), turnspeed * Time.deltaTime);
         transform.position += transform.forward * speed * Time.deltaTime;
         
     }
 }