Server unable to spawn prefab

I have a client and server running for a unity game I'm making. However when I try to instantiate a spell on the client I get this error

 Found no behaviour for incoming [Command:InvokeCmdCmdCastSpell] on Player(Clone) 
 (UnityEngine.GameObject),  the server and client should have the same NetworkBehaviour instances 
 [netId=2].
 UnityEngine.Networking.NetworkIdentity:UNetStaticUpdate()

This is the code I'm using to spawn the spell

 void checkCast(){
     if ((Input.GetMouseButtonDown (0)) && nextcast < Time.time) {
         CmdCastSpell (playerStats.primarySpell);
         stats.primaryCasts += 1;
     }

     if ((Input.GetMouseButtonDown (1)) && nextcast < Time.time) {
         CmdCastSpell (playerStats.secondarySpell);
         stats.secondaryCasts += 1;
     }
 }

 [Command]
 void CmdCastSpell(GameObject spell){
     try{
         SpellControl sc = spell.GetComponent<SpellControl> ();
         if (sc.cost*playerStats.costMultiplier <= playerStats.mana) {
             playerStats.mana -= sc.cost * playerStats.costMultiplier;
             nextcast += sc.reloadTime;
             GameObject s = Instantiate (spell, castPoint.transform.position + castPoint.transform.forward * 2, castPoint.transform.rotation);
             NetworkServer.Spawn (s);
         }
     }catch{
         SpellControlSingle sc = spell.GetComponent<SpellControlSingle> ();
         if (sc.cost*playerStats.costMultiplier <= playerStats.mana) {
             playerStats.mana -= sc.cost * playerStats.costMultiplier;
             nextcast += sc.reloadTime;
             GameObject s = Instantiate (spell, castPoint.transform.position + castPoint.transform.forward * 2, castPoint.transform.rotation);
             NetworkServer.Spawn (s);
         }        
     }
 }

The try catch is just a way to keep single player in the game at the moment

Also both primarySpell and secondarySpell are register with the Network Manager as spawnable prefabs