Plugin Help WorldGuard Error

When I try to install WorldGuard, an error appeared so I can't install it!
Error:

Code:

[16:45:54 ERROR]: Could not load 'plugins\worldguard-6.1.jar' in folder 'plugins'
org.bukkit.plugin.InvalidPluginException: java.lang.NoClassDefFoundError: com/sk89q/minecraft/util/commands/CommandsManager
        at org.bukkit.plugin.java.JavaPluginLoader.loadPlugin(JavaPluginLoader.java:135) ~[craftbukkit.jar:git-Spigot-f928e7a-e91aed8]
        at org.bukkit.plugin.SimplePluginManager.loadPlugin(SimplePluginManager.java:329) ~[craftbukkit.jar:git-Spigot-f928e7a-e91aed8]
        at org.bukkit.plugin.SimplePluginManager.loadPlugins(SimplePluginManager.java:251) [craftbukkit.jar:git-Spigot-f928e7a-e91aed8]
        at org.bukkit.craftbukkit.v1_8_R3.CraftServer.loadPlugins(CraftServer.java:291) [craftbukkit.jar:git-Spigot-f928e7a-e91aed8]
        at org.bukkit.craftbukkit.v1_8_R3.CraftServer.reload(CraftServer.java:740) [craftbukkit.jar:git-Spigot-f928e7a-e91aed8]
        at org.bukkit.Bukkit.reload(Bukkit.java:534) [craftbukkit.jar:git-Spigot-f928e7a-e91aed8]
        at org.bukkit.command.defaults.ReloadCommand.execute(ReloadCommand.java:25) [craftbukkit.jar:git-Spigot-f928e7a-e91aed8]
        at org.bukkit.command.SimpleCommandMap.dispatch(SimpleCommandMap.java:141) [craftbukkit.jar:git-Spigot-f928e7a-e91aed8]
        at org.bukkit.craftbukkit.v1_8_R3.CraftServer.dispatchCommand(CraftServer.java:642) [craftbukkit.jar:git-Spigot-f928e7a-e91aed8]
        at org.bukkit.craftbukkit.v1_8_R3.CraftServer.dispatchServerCommand(CraftServer.java:628) [craftbukkit.jar:git-Spigot-f928e7a-e91aed8]
        at net.minecraft.server.v1_8_R3.DedicatedServer.aO(DedicatedServer.java:404) [craftbukkit.jar:git-Spigot-f928e7a-e91aed8]
        at net.minecraft.server.v1_8_R3.DedicatedServer.B(DedicatedServer.java:368) [craftbukkit.jar:git-Spigot-f928e7a-e91aed8]
        at net.minecraft.server.v1_8_R3.MinecraftServer.A(MinecraftServer.java:657) [craftbukkit.jar:git-Spigot-f928e7a-e91aed8]
        at net.minecraft.server.v1_8_R3.MinecraftServer.run(MinecraftServer.java:560) [craftbukkit.jar:git-Spigot-f928e7a-e91aed8]
        at java.lang.Thread.run(Unknown Source) [?:1.8.0_51]
Caused by: java.lang.NoClassDefFoundError: com/sk89q/minecraft/util/commands/CommandsManager
        at java.lang.Class.forName0(Native Method) ~[?:1.8.0_51]
        at java.lang.Class.forName(Unknown Source) ~[?:1.8.0_51]
        at org.bukkit.plugin.java.PluginClassLoader.<init>(PluginClassLoader.java:64) ~[craftbukkit.jar:git-Spigot-f928e7a-e91aed8]
        at org.bukkit.plugin.java.JavaPluginLoader.loadPlugin(JavaPluginLoader.java:131) ~[craftbukkit.jar:git-Spigot-f928e7a-e91aed8]
        ... 14 more
Caused by: java.lang.ClassNotFoundException: com.sk89q.minecraft.util.commands.CommandsManager
        at java.net.URLClassLoader.findClass(Unknown Source) ~[?:1.8.0_51]
        at org.bukkit.plugin.java.PluginClassLoader.findClass(PluginClassLoader.java:101) ~[craftbukkit.jar:git-Spigot-f928e7a-e91aed8]
        at org.bukkit.plugin.java.PluginClassLoader.findClass(PluginClassLoader.java:86) ~[craftbukkit.jar:git-Spigot-f928e7a-e91aed8]
        at java.lang.ClassLoader.loadClass(Unknown Source) ~[?:1.8.0_51]
        at java.lang.ClassLoader.loadClass(Unknown Source) ~[?:1.8.0_51]
        at java.lang.Class.forName0(Native Method) ~[?:1.8.0_51]
        at java.lang.Class.forName(Unknown Source) ~[?:1.8.0_51]
        at org.bukkit.plugin.java.PluginClassLoader.<init>(PluginClassLoader.java:64) ~[craftbukkit.jar:git-Spigot-f928e7a-e91aed8]
        at org.bukkit.plugin.java.JavaPluginLoader.loadPlugin(JavaPluginLoader.java:131) ~[craftbukkit.jar:git-Spigot-f928e7a-e91aed8]
        ... 14 more

 

Are you still having this issue? Has anyone been able to fix it?

 

he doesn't have worldedit installed