Stuck with - Invalid Cast Exception

Hello,

I'm currently stuck with an issue and cannot seem to find an answer, any help would be great.

I keep getting "InvalidCastException: Specified cast is not valid" with my buffing system.

Error from line: healOverTime = (HealOverTime)buff;

 private HealOverTime healOverTime;
 
         public HealOverTimeBuff(float duration, ScriptableBuff buff, GameObject obj, float tickRate) : base(duration, buff, obj, tickRate)
         {
             this.character = obj.GetComponent<Character>();
             if (this.character == null)
             {
                 End();
                 return;
             }
             healOverTime = (HealOverTime)buff;
         }

HealOverTime inherits from ScriptableBuff class.

Thanks!