NormalizedDrops v1.2.3

09:12:00 [SEVERE] Error occurred while enabling NormalizedDrops v1.2.3 (Is it up to date?)
java.lang.NoClassDefFoundError: org/bukkit/event/entity/EntityListener
        at java.lang.ClassLoader.defineClass1(Native Method)
        at java.lang.ClassLoader.defineClass(Unknown Source)
        at java.security.SecureClassLoader.defineClass(Unknown Source)
        at java.net.URLClassLoader.defineClass(Unknown Source)
        at java.net.URLClassLoader.access$100(Unknown Source)
        at java.net.URLClassLoader$1.run(Unknown Source)
        at java.net.URLClassLoader$1.run(Unknown Source)
        at java.security.AccessController.doPrivileged(Native Method)
        at java.net.URLClassLoader.findClass(Unknown Source)
        at org.bukkit.plugin.java.PluginClassLoader.findClass(PluginClassLoader.java:41)
        at org.bukkit.plugin.java.JavaPluginLoader.getClassByName(JavaPluginLoader.java:239)
        at org.bukkit.plugin.java.PluginClassLoader.findClass(PluginClassLoader.java:37)
        at org.bukkit.plugin.java.PluginClassLoader.findClass(PluginClassLoader.java:29)
        at java.lang.ClassLoader.loadClass(Unknown Source)
        at java.lang.ClassLoader.loadClass(Unknown Source)
        at com.minecarts.normalizeddrops.NormalizedDrops.onEnable(NormalizedDrops.java:49)
        at org.bukkit.plugin.java.JavaPlugin.setEnabled(JavaPlugin.java:215)
        at org.bukkit.plugin.java.JavaPluginLoader.enablePlugin(JavaPluginLoader.java:343)
        at org.bukkit.plugin.SimplePluginManager.enablePlugin(SimplePluginManager.java:364)
        at org.bukkit.craftbukkit.CraftServer.loadPlugin(CraftServer.java:225)
        at org.bukkit.craftbukkit.CraftServer.enablePlugins(CraftServer.java:208)
        at net.minecraft.server.MinecraftServer.t(MinecraftServer.java:357)
        at net.minecraft.server.MinecraftServer.a(MinecraftServer.java:344)
        at net.minecraft.server.MinecraftServer.init(MinecraftServer.java:175)
        at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:408)
        at net.minecraft.server.ThreadServerApplication.run(SourceFile:465)
Caused by: java.lang.ClassNotFoundException: org.bukkit.event.entity.EntityListener
        at java.net.URLClassLoader$1.run(Unknown Source)
        at java.net.URLClassLoader$1.run(Unknown Source)
        at java.security.AccessController.doPrivileged(Native Method)
        at java.net.URLClassLoader.findClass(Unknown Source)
        at org.bukkit.plugin.java.PluginClassLoader.findClass(PluginClassLoader.java:41)
        at org.bukkit.plugin.java.PluginClassLoader.findClass(PluginClassLoader.java:29)
        at java.lang.ClassLoader.loadClass(Unknown Source)
        at java.lang.ClassLoader.loadClass(Unknown Source)
        ... 26 more