Server.log

[SEVERE] Could not pass event SkillUseEvent to HeroesSkillTree v1.5.2-Beta
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.TimedRegisteredListener.callEvent(TimedRegisteredListener.java:47)
	at org.bukkit.plugin.SimplePluginManager.fireEvent(SimplePluginManager.java:478)
	at org.bukkit.plugin.SimplePluginManager.callEvent(SimplePluginManager.java:463)
	at com.herocraftonline.heroes.characters.skill.ActiveSkill.execute(ActiveSkill.java:155)
	at com.herocraftonline.heroes.command.CommandHandler.dispatch(CommandHandler.java:73)
	at com.herocraftonline.heroes.listeners.HPlayerListener.onPlayerInteract(HPlayerListener.java:205)
	at sun.reflect.GeneratedMethodAccessor74.invoke(Unknown Source)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
	at java.lang.reflect.Method.invoke(Unknown Source)
	at org.bukkit.plugin.java.JavaPluginLoader$1.execute(JavaPluginLoader.java:425)
	at org.bukkit.plugin.RegisteredListener.callEvent(RegisteredListener.java:62)
	at org.bukkit.plugin.TimedRegisteredListener.callEvent(TimedRegisteredListener.java:47)
	at org.bukkit.plugin.SimplePluginManager.fireEvent(SimplePluginManager.java:478)
	at org.bukkit.plugin.SimplePluginManager.callEvent(SimplePluginManager.java:463)
	at org.bukkit.craftbukkit.v1_6_R3.event.CraftEventFactory.callPlayerInteractEvent(CraftEventFactory.java:207)
	at net.minecraft.server.v1_6_R3.PlayerInteractManager.interact(PlayerInteractManager.java:374)
	at net.minecraft.server.v1_6_R3.PlayerConnection.a(PlayerConnection.java:631)
	at net.minecraft.server.v1_6_R3.Packet15Place.handle(SourceFile:58)
	at org.spigotmc.netty.NettyNetworkManager.b(NettyNetworkManager.java:230)
	at net.minecraft.server.v1_6_R3.PlayerConnection.e(PlayerConnection.java:117)
	at net.minecraft.server.v1_6_R3.ServerConnection.b(SourceFile:37)
	at org.spigotmc.netty.NettyServerConnection.b(NettyServerConnection.java:132)
	at net.minecraft.server.v1_6_R3.MinecraftServer.t(MinecraftServer.java:594)
	at net.minecraft.server.v1_6_R3.DedicatedServer.t(DedicatedServer.java:240)
	at net.minecraft.server.v1_6_R3.MinecraftServer.s(MinecraftServer.java:483)
	at net.minecraft.server.v1_6_R3.MinecraftServer.run(MinecraftServer.java:415)
	at net.minecraft.server.v1_6_R3.ThreadServerApplication.run(SourceFile:583)
Caused by: java.lang.NoSuchMethodError: com.herocraftonline.heroes.api.events.SkillUseEvent.getHealthCost()I
	at me.Whatshiywl.heroesskilltree.EventListener.onPlayerUseSkill(EventListener.java:153)
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
	at java.lang.reflect.Method.invoke(Unknown Source)
	at org.bukkit.plugin.java.JavaPluginLoader$1.execute(JavaPluginLoader.java:425)
	... 28 more