MythicMobs bug

>.... [20:23:22 ERROR]: Error occurred while enabling MythicMobs v4.9.0-SNAPSHOT-3170 (Is it up to date?)
java.lang.IllegalArgumentException: No enum constant org.bukkit.Material.OAK_BARK
at java.lang.Enum.valueOf(Enum.java:238) ~[?:1.8.0_222]
at org.bukkit.Material.valueOf(Material.java:84) ~[patched_1.15.1.jar:git-Paper-60]
at io.lumine.xikage.mythicmobs.items.LegacyItemConverter.getMaterialByKey(LegacyItemConverter.java:49) ~[?:?]
at io.lumine.xikage.mythicmobs.items.LegacyItemConverter.getMaterial(LegacyItemConverter.java:58) ~[?:?]
at io.lumine.xikage.mythicmobs.drops.Drop.getDrop(Drop.java:165) ~[?:?]
at io.lumine.xikage.mythicmobs.drops.DropTable.lambda$new$1(DropTable.java:93) ~[?:?]
at io.lumine.xikage.mythicmobs.drops.DropTable$$Lambda$3884.00000000FEDF8E90.run(Unknown Source) ~[?:?]
at io.lumine.xikage.mythicmobs.drops.DropManager.lambda$runSecondPass$0(DropManager.java:62) ~[?:?]
at io.lumine.xikage.mythicmobs.drops.DropManager$$Lambda$3893.00000000FD5B6800.accept(Unknown Source) ~[?:?]
at java.util.ArrayList.forEach(ArrayList.java:1257) ~[?:1.8.0_222]
at io.lumine.xikage.mythicmobs.drops.DropManager.runSecondPass(DropManager.java:62) ~[?:?]
at io.lumine.xikage.mythicmobs.drops.DropManager.loadDropTables(DropManager.java:55) ~[?:?]
at io.lumine.xikage.mythicmobs.io.ConfigManager.LoadAll(ConfigManager.java:106) ~[?:?]
at io.lumine.xikage.mythicmobs.MythicMobs.onEnable(MythicMobs.java:142) ~[?:?]
at org.bukkit.plugin.java.JavaPlugin.setEnabled(JavaPlugin.java:263) ~[patched_1.15.1.jar:git-Paper-60]
at org.bukkit.plugin.java.JavaPluginLoader.enablePlugin(JavaPluginLoader.java:338) ~[patched_1.15.1.jar:git-Paper-60]
at org.bukkit.plugin.SimplePluginManager.enablePlugin(SimplePluginManager.java:420) ~[patched_1.15.1.jar:git-Paper-60]
at org.bukkit.craftbukkit.v1_15_R1.CraftServer.enablePlugin(CraftServer.java:468) ~[patched_1.15.1.jar:git-Paper-60]
at org.bukkit.craftbukkit.v1_15_R1.CraftServer.enablePlugins(CraftServer.java:382) ~[patched_1.15.1.jar:git-Paper-60]
at net.minecraft.server.v1_15_R1.MinecraftServer.a(MinecraftServer.java:481) ~[patched_1.15.1.jar:git-Paper-60]
at net.minecraft.server.v1_15_R1.DedicatedServer.init(DedicatedServer.java:290) ~[patched_1.15.1.jar:git-Paper-60]
at net.minecraft.server.v1_15_R1.MinecraftServer.run(MinecraftServer.java:884) ~[patched_1.15.1.jar:git-Paper-60]
at java.lang.Thread.run(Thread.java:819) [?:1.8.0_222]
>.... [20:23:22 INFO]: [MythicMobs] Disabling MythicMobs v4.9.0-SNAPSHOT-3170
>.... [20:23:22 INFO]: [MythicMobs] Disabling Mythic Mobs...
>.... [20:23:22 INFO]: [MythicMobs] All active settings have been saved.
>.... [20:23:22 INFO]: [MythicMobs] v4.9.0-SNAPSHOT-3170 has been Disabled!