diff --git a/src/engine/ai/MobileFSM.java b/src/engine/ai/MobileFSM.java
index 1a28339a..809ac396 100644
--- a/src/engine/ai/MobileFSM.java
+++ b/src/engine/ai/MobileFSM.java
@@ -1648,6 +1648,7 @@ public class MobileFSM {
         // if done previously in canCast();
 
         ArrayList<Integer> powerTokens;
+        ArrayList<Integer> purgeTokens;
         PlayerCharacter target = (PlayerCharacter) mob.getCombatTarget();
 
         if (mob.getMobBase().getFlags().contains(Enum.MobFlagType.CALLSFORHELP))
@@ -1656,9 +1657,10 @@ public class MobileFSM {
         // Generate a list of tokens from the mob powers for this mobile.
 
         powerTokens = new ArrayList<>(mob.mobPowers.keySet());
+        purgeTokens = new ArrayList<>();
 
         // If player has this effect on them already then remove the token
-        // from the list of mob powers
+        // from our list of mob powers
 
         for (int powerToken : powerTokens){
 
@@ -1669,10 +1671,12 @@ public class MobileFSM {
                 String des = act.stackType;
 
                 if (target.getEffects() != null && target.getEffects().containsKey(des))
-                    powerTokens.remove(Integer.valueOf(powerToken));
+                    purgeTokens.add(powerToken);
             }
         }
 
+        powerTokens.removeAll(purgeTokens);
+
         // Pick random spell from our list of powers
 
         int powerToken = powerTokens.get(ThreadLocalRandom.current().nextInt(powerTokens.size()));