ServerListPlus 3.3.3 - Error on Spigot 1.8.3R0.1

[21:55:07] [Server thread/INFO]: [ServerListPlus] Enabling ServerListPlus v3.3.3
[21:55:07] [Server thread/INFO]: [ServerListPlus] Starting...
[21:55:07] [Server thread/ERROR]: Error occurred while enabling ServerListPlus v3.3.3 (Is it up to date?)
java.lang.NoClassDefFoundError: com/google/gson/JsonSyntaxException
    at net.minecrell.serverlistplus.bukkit.core.ServerListPlusCore.<init>(ServerListPlusCore.java:105) ~[?:?]
    at net.minecrell.serverlistplus.bukkit.BukkitPlugin.onEnable(BukkitPlugin.java:129) ~[?:?]
    at org.bukkit.plugin.java.JavaPlugin.setEnabled(JavaPlugin.java:321) ~[server.jar:git-Spigot-c3c767f-33d5de3]
    at org.bukkit.plugin.java.JavaPluginLoader.enablePlugin(JavaPluginLoader.java:335) [server.jar:git-Spigot-c3c767f-33d5de3]
    at org.bukkit.plugin.SimplePluginManager.enablePlugin(SimplePluginManager.java:405) [server.jar:git-Spigot-c3c767f-33d5de3]
    at org.bukkit.craftbukkit.v1_8_R1.CraftServer.loadPlugin(CraftServer.java:356) [server.jar:git-Spigot-c3c767f-33d5de3]
    at org.bukkit.craftbukkit.v1_8_R1.CraftServer.enablePlugins(CraftServer.java:316) [server.jar:git-Spigot-c3c767f-33d5de3]
    at net.minecraft.server.v1_8_R1.MinecraftServer.q(MinecraftServer.java:402) [server.jar:git-Spigot-c3c767f-33d5de3]
    at net.minecraft.server.v1_8_R1.MinecraftServer.k(MinecraftServer.java:370) [server.jar:git-Spigot-c3c767f-33d5de3]
    at net.minecraft.server.v1_8_R1.MinecraftServer.a(MinecraftServer.java:325) [server.jar:git-Spigot-c3c767f-33d5de3]
    at net.minecraft.server.v1_8_R1.DedicatedServer.init(DedicatedServer.java:211) [server.jar:git-Spigot-c3c767f-33d5de3]
    at net.minecraft.server.v1_8_R1.MinecraftServer.run(MinecraftServer.java:505) [server.jar:git-Spigot-c3c767f-33d5de3]
    at java.lang.Thread.run(Thread.java:745) [?:1.7.0_75]
Caused by: java.lang.ClassNotFoundException: com.google.gson.JsonSyntaxException
    at java.net.URLClassLoader$1.run(URLClassLoader.java:366) ~[?:1.7.0_75]
    at java.net.URLClassLoader$1.run(URLClassLoader.java:355) ~[?:1.7.0_75]
    at java.security.AccessController.doPrivileged(Native Method) ~[?:1.7.0_75]
    at java.net.URLClassLoader.findClass(URLClassLoader.java:354) ~[?:1.7.0_75]
    at org.bukkit.plugin.java.PluginClassLoader.findClass(PluginClassLoader.java:101) ~[server.jar:git-Spigot-c3c767f-33d5de3]
    at org.bukkit.plugin.java.PluginClassLoader.findClass(PluginClassLoader.java:86) ~[server.jar:git-Spigot-c3c767f-33d5de3]
    at java.lang.ClassLoader.loadClass(ClassLoader.java:425) ~[?:1.7.0_75]
    at java.lang.ClassLoader.loadClass(ClassLoader.java:358) ~[?:1.7.0_75]
    ... 13 more