StartCoroutine & WaitForSeconds Error

I'm currently working on a clicker game but when ever I try and use a StartCoroutine for my autoticker it gives me the following two errors:

1: Assets/Scripts/GoldPerSec.cs(12,17): error CS1502: The best overloaded method match for UnityEngine.MonoBehaviour.StartCoroutine(System.Collections.IEnumerator) has some invalid arguments

2: Assets/Scripts/GoldPerSec.cs(12,17): error CS1503: Argument #1 cannot convert System.Collections.IEnumerable expression to type `System.Collections.IEnumerator'

 using UnityEngine;
 using System.Collections;
 
 public class GoldPerSec : MonoBehaviour {
 
     public UnityEngine.UI.Text gpsDisplay;
     public Click click;
     public ItemManager[] items;
 
     // Use this for initialization
     void Start () {
         StartCoroutine(AutoTick());
     }
     
     // Update is called once per frame
     void Update () {
         gpsDisplay.text = GetGoldPerSec() + " gold/sec";
         
     }
 
     public int GetGoldPerSec(){
         int tick = 0;
         foreach(ItemManager item in items){
             tick += item.count * item.tickValue;
         }
         return tick;
     }
 
     public void AutoGoldPerSec(){
         click.gold += GetGoldPerSec();
     }
 
     IEnumerable AutoTick(){
         while(true){
             AutoGoldPerSec();
             yield return new WaitForSeconds(1);
         }
     }
 }