Elemental Swords debug output

13:36:59 [SEVERE] Could not pass event PlayerJoinEvent to ElementalSwords v0.4.7
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 net.minecraft.server.v1_5_R2.PlayerList.c(PlayerList.java:205)
        at net.minecraft.server.v1_5_R2.PlayerList.a(PlayerList.java:101)
        at net.minecraft.server.v1_5_R2.PendingConnection.d(PendingConnection.java:129)
        at net.minecraft.server.v1_5_R2.PendingConnection.c(PendingConnection.java:44)
        at net.minecraft.server.v1_5_R2.DedicatedServerConnectionThread.a(DedicatedServerConnectionThread.java:41)
        at net.minecraft.server.v1_5_R2.DedicatedServerConnection.b(SourceFile:29)
        at net.minecraft.server.v1_5_R2.MinecraftServer.r(MinecraftServer.java:580)
        at net.minecraft.server.v1_5_R2.DedicatedServer.r(DedicatedServer.java:225)
        at net.minecraft.server.v1_5_R2.MinecraftServer.q(MinecraftServer.java:476)
        at net.minecraft.server.v1_5_R2.MinecraftServer.run(MinecraftServer.java:409)
        at net.minecraft.server.v1_5_R2.ThreadServerApplication.run(SourceFile:573)
Caused by: java.lang.NoClassDefFoundError: net/minecraft/server/v1_5_R1/PlayerConnection
        at java.lang.ClassLoader.defineClass1(Native Method)
        at java.lang.ClassLoader.defineClass(ClassLoader.java:787)
        at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:142)
        at java.net.URLClassLoader.defineClass(URLClassLoader.java:447)
        at java.net.URLClassLoader.access$100(URLClassLoader.java:71)
        at java.net.URLClassLoader$1.run(URLClassLoader.java:361)
        at java.net.URLClassLoader$1.run(URLClassLoader.java:355)
        at java.security.AccessController.doPrivileged(Native Method)
        at java.net.URLClassLoader.findClass(URLClassLoader.java:354)
        at org.bukkit.plugin.java.PluginClassLoader.findClass0(PluginClassLoader.java:80)
        at org.bukkit.plugin.java.JavaPluginLoader.getClassByName0(JavaPluginLoader.java:300)
        at org.bukkit.plugin.java.PluginClassLoader.findClass0(PluginClassLoader.java:76)
        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)
        at elementalSwords.listeners.AttackListener.onPlayerJoin(AttackListener.java:62)
        at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
        at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
        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)
        ... 14 more
Caused by: java.lang.ClassNotFoundException: net.minecraft.server.v1_5_R1.PlayerConnection
        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)
        ... 35 more