diff --git a/MobArena.jar b/MobArena.jar
index 20a5926..2e70bbc 100644
Binary files a/MobArena.jar and b/MobArena.jar differ
diff --git a/src/com/garbagemule/MobArena/Arena.java b/src/com/garbagemule/MobArena/Arena.java
index 1d64f0d..e701687 100644
--- a/src/com/garbagemule/MobArena/Arena.java
+++ b/src/com/garbagemule/MobArena/Arena.java
@@ -300,7 +300,7 @@ public class Arena
             playerLeave(p);
         
         for (Entity e : monsters)
-            e.remove();
+            if (e != null) e.remove();
         
         if (bossWave != null)
             bossWave.clear();
@@ -465,6 +465,8 @@ public class Arena
                     
                     for (LivingEntity e : new LinkedList<LivingEntity>(explodingSheep))
                     {
+                        if (e == null) continue;
+                        
                         Creature c = (Creature) e;
                         if (c.getTarget() != null && e.getLocation().distanceSquared(c.getTarget().getLocation()) < 8)
                         {
@@ -777,13 +779,13 @@ public class Arena
         if (bossWave != null)
             bossWave.clear();
         for (LivingEntity e : monsters)
-            e.remove();
+            if (e != null) e.remove();
         for (LivingEntity e : explodingSheep)
-            e.remove();
+            if (e != null) e.remove();
         for (LivingEntity e : plaguedPigs)
-            e.remove();
+            if (e != null) e.remove();
         for (LivingEntity e : madCows)
-            e.remove();
+            if (e != null) e.remove();
     }
     
     private void removeBlocks()
@@ -796,6 +798,8 @@ public class Arena
     {
         for (Wolf w : pets)
         {
+            if (w == null) continue;
+            
             w.setOwner(null);
             w.remove();
         }
@@ -805,7 +809,7 @@ public class Arena
     {
         for (Wolf w : pets)
         {
-            if (!((Player) w.getOwner()).getName().equals(p.getName()))
+            if (w == null || !((Player) w.getOwner()).getName().equals(p.getName()))
                 continue;
             
             w.setOwner(null);
@@ -824,7 +828,7 @@ public class Arena
             for (int j = c1.getZ(); j <= c2.getZ(); j++)
                 for (Entity e : world.getChunkAt(i,j).getEntities())
                     if ((e instanceof Item || e instanceof Slime) && inRegion(e.getLocation()))
-                        e.remove();
+                        if (e != null) e.remove();
     }
     
     
diff --git a/src/com/garbagemule/MobArena/MASpawnThread.java b/src/com/garbagemule/MobArena/MASpawnThread.java
index 29afac9..1160740 100644
--- a/src/com/garbagemule/MobArena/MASpawnThread.java
+++ b/src/com/garbagemule/MobArena/MASpawnThread.java
@@ -87,6 +87,8 @@ public class MASpawnThread implements Runnable
         List<Entity> tmp = new LinkedList<Entity>(arena.monsters);
         for (Entity e : tmp)
         {
+            if (e == null) continue;
+            
             if (e.isDead() || !arena.inRegion(e.getLocation()))
             {
                 arena.monsters.remove(e);
@@ -230,6 +232,8 @@ public class MASpawnThread implements Runnable
         Location loc;
         for (Entity e : tmp)
         {
+            if (e == null) continue;
+            
             arena.monsters.remove(e);
             loc = e.getLocation().getBlock().getRelative(0,2,0).getLocation();
             arena.world.createExplosion(loc, 2);
diff --git a/src/com/garbagemule/MobArena/waves/AbstractWave.java b/src/com/garbagemule/MobArena/waves/AbstractWave.java
index ebb791c..d42918b 100644
--- a/src/com/garbagemule/MobArena/waves/AbstractWave.java
+++ b/src/com/garbagemule/MobArena/waves/AbstractWave.java
@@ -84,8 +84,11 @@ public abstract class AbstractWave implements Wave
      */
     public LivingEntity spawnMonster(MACreature creature, Location loc)
     {
-        // Spawn and add to collection
+        // Spawn
         LivingEntity e = creature.spawn(getArena(), getWorld(), loc);
+        if (e == null) return null;
+        
+        // Add to collection
         getArena().addMonster(e);
         
         // Boost health
diff --git a/src/com/garbagemule/MobArena/waves/BossWave.java b/src/com/garbagemule/MobArena/waves/BossWave.java
index d839d54..f58f031 100644
--- a/src/com/garbagemule/MobArena/waves/BossWave.java
+++ b/src/com/garbagemule/MobArena/waves/BossWave.java
@@ -135,6 +135,8 @@ public class BossWave extends AbstractWave
         cancelAbilityTask();
         getArena().setBossWave(null);
         
+        if (bossCreature == null) return;
+            
         CraftEntity ce = (CraftEntity) bossCreature;
         CraftWorld cw = (CraftWorld) getWorld();
         WorldServer ws = cw.getHandle();
diff --git a/src/com/garbagemule/MobArena/waves/SwarmWave.java b/src/com/garbagemule/MobArena/waves/SwarmWave.java
index ca0b2fe..ed2ec1f 100644
--- a/src/com/garbagemule/MobArena/waves/SwarmWave.java
+++ b/src/com/garbagemule/MobArena/waves/SwarmWave.java
@@ -65,6 +65,7 @@ public class SwarmWave extends AbstractWave
         for (int i = 0; i < amount; i++)
         {
             LivingEntity e = spawnMonster(monster, spawnpoints.get(i % spawnpointCount));
+            if (e == null) continue;
             
             // Boost health
             int health = (int) Math.min(150D, 1 * getHealthMultiplier());