Prism Error - NoClassDefFound GsonBuilder

Could not pass event PlayerCommandPreprocessEvent to Prism v2.0.6-25
org.bukkit.event.EventException
        at org.bukkit.plugin.java.JavaPluginLoader$1.execute(JavaPluginLoader.java:305) ~[spigot.jar:git-Spigot-8a983f9-e81edfc]
        at org.bukkit.plugin.RegisteredListener.callEvent(RegisteredListener.java:62) ~[spigot.jar:git-Spigot-8a983f9-e81edfc]
        at org.bukkit.plugin.SimplePluginManager.fireEvent(SimplePluginManager.java:502) [spigot.jar:git-Spigot-8a983f9-e81edfc]
        at org.bukkit.plugin.SimplePluginManager.callEvent(SimplePluginManager.java:487) [spigot.jar:git-Spigot-8a983f9-e81edfc]
        at net.minecraft.server.v1_8_R1.PlayerConnection.handleCommand(PlayerConnection.java:1107) [spigot.jar:git-Spigot-8a983f9-e81edfc]
        at net.minecraft.server.v1_8_R1.PlayerConnection.a(PlayerConnection.java:950) [spigot.jar:git-Spigot-8a983f9-e81edfc]
        at net.minecraft.server.v1_8_R1.PacketPlayInChat.a(PacketPlayInChat.java:26) [spigot.jar:git-Spigot-8a983f9-e81edfc]
        at net.minecraft.server.v1_8_R1.PacketPlayInChat.a(PacketPlayInChat.java:53) [spigot.jar:git-Spigot-8a983f9-e81edfc]
        at net.minecraft.server.v1_8_R1.PacketHandleTask.run(SourceFile:13) [spigot.jar:git-Spigot-8a983f9-e81edfc]
        at java.util.concurrent.Executors$RunnableAdapter.call(Unknown Source) [?:1.8.0_25]
        at java.util.concurrent.FutureTask.run(Unknown Source) [?:1.8.0_25]
        at net.minecraft.server.v1_8_R1.MinecraftServer.z(MinecraftServer.java:696) [spigot.jar:git-Spigot-8a983f9-e81edfc]
        at net.minecraft.server.v1_8_R1.DedicatedServer.z(DedicatedServer.java:316) [spigot.jar:git-Spigot-8a983f9-e81edfc]
        at net.minecraft.server.v1_8_R1.MinecraftServer.y(MinecraftServer.java:634) [spigot.jar:git-Spigot-8a983f9-e81edfc]
        at net.minecraft.server.v1_8_R1.MinecraftServer.run(MinecraftServer.java:537) [spigot.jar:git-Spigot-8a983f9-e81edfc]
        at java.lang.Thread.run(Unknown Source) [?:1.8.0_25]
Caused by: java.lang.NoClassDefFoundError: com/google/gson/GsonBuilder
        at me.botsko.prism.actions.GenericAction.<init>(GenericAction.java:34) ~[?:?]
        at me.botsko.prism.actions.PlayerAction.<init>(PlayerAction.java:3) ~[?:?]
        at me.botsko.prism.actionlibs.ActionFactory.createPlayer(ActionFactory.java:202) ~[?:?]
        at me.botsko.prism.listeners.PrismPlayerEvents.onCommandPreprocess(PrismPlayerEvents.java:109) ~[?:?]
        at sun.reflect.GeneratedMethodAccessor39.invoke(Unknown Source) ~[?:?]
        at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source) ~[?:1.8.0_25]
        at java.lang.reflect.Method.invoke(Unknown Source) ~[?:1.8.0_25]
        at org.bukkit.plugin.java.JavaPluginLoader$1.execute(JavaPluginLoader.java:301) ~[spigot.jar:git-Spigot-8a983f9-e81edfc]
        ... 15 more