Error

[08:30:01] [Server thread/ERROR]: Error occurred while enabling Quests v2.5.0-b80 (Is it up to date?)
java.lang.NoClassDefFoundError: net/citizensnpcs/api/CitizensPlugin
	at me.blackvein.quests.Quests.linkOtherPlugins(Quests.java:398) ~[?:?]
	at me.blackvein.quests.Quests.onEnable(Quests.java:182) ~[?:?]
	at org.bukkit.plugin.java.JavaPlugin.setEnabled(JavaPlugin.java:321) ~[spigot35.jar:git-Spigot-dbe012b-63e28b1]
	at org.bukkit.plugin.java.JavaPluginLoader.enablePlugin(JavaPluginLoader.java:335) [spigot35.jar:git-Spigot-dbe012b-63e28b1]
	at org.bukkit.plugin.SimplePluginManager.enablePlugin(SimplePluginManager.java:405) [spigot35.jar:git-Spigot-dbe012b-63e28b1]
	at org.bukkit.craftbukkit.v1_8_R2.CraftServer.loadPlugin(CraftServer.java:356) [spigot35.jar:git-Spigot-dbe012b-63e28b1]
	at org.bukkit.craftbukkit.v1_8_R2.CraftServer.enablePlugins(CraftServer.java:316) [spigot35.jar:git-Spigot-dbe012b-63e28b1]
	at net.minecraft.server.v1_8_R2.MinecraftServer.r(MinecraftServer.java:416) [spigot35.jar:git-Spigot-dbe012b-63e28b1]
	at net.minecraft.server.v1_8_R2.MinecraftServer.k(MinecraftServer.java:382) [spigot35.jar:git-Spigot-dbe012b-63e28b1]
	at net.minecraft.server.v1_8_R2.MinecraftServer.a(MinecraftServer.java:337) [spigot35.jar:git-Spigot-dbe012b-63e28b1]
	at net.minecraft.server.v1_8_R2.DedicatedServer.init(DedicatedServer.java:257) [spigot35.jar:git-Spigot-dbe012b-63e28b1]
	at net.minecraft.server.v1_8_R2.MinecraftServer.run(MinecraftServer.java:522) [spigot35.jar:git-Spigot-dbe012b-63e28b1]
	at java.lang.Thread.run(Thread.java:745) [?:1.8.0_31]
Caused by: java.lang.ClassNotFoundException: net.citizensnpcs.api.CitizensPlugin
	at java.net.URLClassLoader$1.run(URLClassLoader.java:372) ~[?:1.8.0_31]
	at java.net.URLClassLoader$1.run(URLClassLoader.java:361) ~[?:1.8.0_31]
	at java.security.AccessController.doPrivileged(Native Method) ~[?:1.8.0_31]
	at java.net.URLClassLoader.findClass(URLClassLoader.java:360) ~[?:1.8.0_31]
	at org.bukkit.plugin.java.PluginClassLoader.findClass(PluginClassLoader.java:101) ~[spigot35.jar:git-Spigot-dbe012b-63e28b1]
	at org.bukkit.plugin.java.PluginClassLoader.findClass(PluginClassLoader.java:86) ~[spigot35.jar:git-Spigot-dbe012b-63e28b1]
	at java.lang.ClassLoader.loadClass(ClassLoader.java:424) ~[?:1.8.0_31]
	at java.lang.ClassLoader.loadClass(ClassLoader.java:357) ~[?:1.8.0_31]
	... 13 more