InfernalMobs bug

[10:40:06 WARN]: [InfernalMobs] Task #3430 for InfernalMobs v3.1 generated an exception
java.lang.NoClassDefFoundError: me/confuser/barapi/BarAPI
        at io.hotmail.com.jacob_vejvoda.infernal_mobs.infernal_mobs.clearInfo(infernal_mobs.java:186) ~[?:?]
        at io.hotmail.com.jacob_vejvoda.infernal_mobs.infernal_mobs.fixBar(infernal_mobs.java:180) ~[?:?]
        at io.hotmail.com.jacob_vejvoda.infernal_mobs.infernal_mobs.showEffect(infernal_mobs.java:933) ~[?:?]
        at io.hotmail.com.jacob_vejvoda.infernal_mobs.infernal_mobs$1.run(infernal_mobs.java:453) ~[?:?]
        at org.bukkit.craftbukkit.v1_7_R4.scheduler.CraftTask.run(CraftTask.java:71) ~[spigot.jar:git-Spigot-1545]
        at org.bukkit.craftbukkit.v1_7_R4.scheduler.CraftScheduler.mainThreadHeartbeat(CraftScheduler.java:346) [spigot.jar:git-Spigot-1545]
        at net.minecraft.server.v1_7_R4.MinecraftServer.v(MinecraftServer.java:638) [spigot.jar:git-Spigot-1545]
        at net.minecraft.server.v1_7_R4.DedicatedServer.v(DedicatedServer.java:289) [spigot.jar:git-Spigot-1545]
        at net.minecraft.server.v1_7_R4.MinecraftServer.u(MinecraftServer.java:584) [spigot.jar:git-Spigot-1545]
        at net.minecraft.server.v1_7_R4.MinecraftServer.run(MinecraftServer.java:490) [spigot.jar:git-Spigot-1545]
        at net.minecraft.server.v1_7_R4.ThreadServerApplication.run(SourceFile:628) [spigot.jar:git-Spigot-1545]