`Description: Exception in server tick loop

java.util.ConcurrentModificationException
at java.util.IdentityHashMap$IdentityHashMapIterator.nextIndex(Unknown Source)
at java.util.IdentityHashMap$EntryIterator.next(Unknown Source)
at java.util.IdentityHashMap$EntryIterator.next(Unknown Source)
at com.infinityraider.boatlantern.lantern.LanternItemCache.onTick(LanternItemCache.java:58)
at net.minecraftforge.fml.common.eventhandler.ASMEventHandler_802_LanternItemCache_onTick_WorldTickEvent.invoke(.dynamic)
at net.minecraftforge.fml.common.eventhandler.ASMEventHandler.invoke(ASMEventHandler.java:90)
at net.minecraftforge.fml.common.eventhandler.EventBus.post(EventBus.java:185)
at net.minecraftforge.fml.common.FMLCommonHandler.onPostWorldTick(FMLCommonHandler.java:269)
at net.minecraft.server.MinecraftServer.func_71190_q(MinecraftServer.java:718)
at net.minecraft.server.MinecraftServer.func_71217_p(MinecraftServer.java:613)
at net.minecraft.server.integrated.IntegratedServer.func_71217_p(IntegratedServer.java:149)
at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:471)
at java.lang.Thread.run(Unknown Source)`

Title says it all.
infinitylib-0.11.0.jar
boatlantern-0.11.0.jar