enchantapi error

19:49:45 [SEVERE] Could not pass event InventoryOpenEvent to EnchantmentAPI v4.8
org.bukkit.event.EventException
        at org.bukkit.plugin.java.JavaPluginLoader$1.execute(JavaPluginLoader.java:427)
        at org.bukkit.plugin.RegisteredListener.callEvent(RegisteredListener.java:62)
        at org.bukkit.plugin.SimplePluginManager.fireEvent(SimplePluginManager.java:477)
        at org.bukkit.plugin.SimplePluginManager.callEvent(SimplePluginManager.java:462)
        at org.bukkit.craftbukkit.v1_6_R1.event.CraftEventFactory.callInventoryOpenEvent(CraftEventFactory.java:554)
        at net.minecraft.server.v1_6_R1.EntityPlayer.openAnvil(EntityPlayer.java:511)
        at net.minecraft.server.v1_6_R1.BlockAnvil.interact(SourceFile:85)
        at net.minecraft.server.v1_6_R1.PlayerInteractManager.interact(PlayerInteractManager.java:382)
        at net.minecraft.server.v1_6_R1.PlayerConnection.a(PlayerConnection.java:649)
        at net.minecraft.server.v1_6_R1.Packet15Place.handle(SourceFile:58)
        at net.minecraft.server.v1_6_R1.NetworkManager.b(NetworkManager.java:293)
        at net.minecraft.server.v1_6_R1.PlayerConnection.d(PlayerConnection.java:118)
        at net.minecraft.server.v1_6_R1.ServerConnection.b(SourceFile:37)
        at net.minecraft.server.v1_6_R1.DedicatedServerConnection.b(SourceFile:30)
        at net.minecraft.server.v1_6_R1.MinecraftServer.t(MinecraftServer.java:590)
        at net.minecraft.server.v1_6_R1.DedicatedServer.t(DedicatedServer.java:226)
        at net.minecraft.server.v1_6_R1.MinecraftServer.s(MinecraftServer.java:486)
        at net.minecraft.server.v1_6_R1.MinecraftServer.run(MinecraftServer.java:419)
        at net.minecraft.server.v1_6_R1.ThreadServerApplication.run(SourceFile:582)
Caused by: java.lang.NoClassDefFoundError: org/bukkit/craftbukkit/v1_5_R3/inventory/CraftItemStack
        at com.rit.sucy.Anvil.AnvilListener.onOpen(AnvilListener.java:42)
        at sun.reflect.GeneratedMethodAccessor356.invoke(Unknown Source)
        at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
        at java.lang.reflect.Method.invoke(Method.java:601)
        at org.bukkit.plugin.java.JavaPluginLoader$1.execute(JavaPluginLoader.java:425)
        ... 18 more
Caused by: java.lang.ClassNotFoundException: org.bukkit.craftbukkit.v1_5_R3.inventory.CraftItemStack
        at org.bukkit.plugin.java.PluginClassLoader.findClass0(PluginClassLoader.java:70)
        at org.bukkit.plugin.java.PluginClassLoader.findClass(PluginClassLoader.java:53)
        at java.lang.ClassLoader.loadClass(ClassLoader.java:423)
        at java.lang.ClassLoader.loadClass(ClassLoader.java:356)
        ... 23 more