I get this spam in the log. Disabling the compatibility fixes the problem.
[11:05:19] [Server thread/FATAL] [net.minecraft.server.MinecraftServer]: Error executing task
java.util.concurrent.ExecutionException: java.lang.NoClassDefFoundError: p455w0rd/danknull/util/DankNullUtils
at java.util.concurrent.FutureTask.report(Unknown Source) ~[?:1.8.0_191]
at java.util.concurrent.FutureTask.get(Unknown Source) ~[?:1.8.0_191]
at net.minecraft.util.Util.func_181617_a(SourceFile:47) [h.class:?]
at net.minecraft.server.MinecraftServer.func_71190_q(MinecraftServer.java:723) [MinecraftServer.class:?]
at net.minecraft.server.MinecraftServer.func_71217_p(MinecraftServer.java:668) [MinecraftServer.class:?]
at net.minecraft.server.integrated.IntegratedServer.func_71217_p(IntegratedServer.java:185) [chd.class:?]
at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:526) [MinecraftServer.class:?]
at java.lang.Thread.run(Unknown Source) [?:1.8.0_191]
Caused by: java.lang.NoClassDefFoundError: p455w0rd/danknull/util/DankNullUtils
at exnihilocreatio.blocks.BlockSieve.func_180639_a(BlockSieve.java:83) ~[BlockSieve.class:?]
at net.minecraft.server.management.PlayerInteractionManager.func_187251_a(PlayerInteractionManager.java:449) ~[or.class:?]
at net.minecraft.network.NetHandlerPlayServer.func_184337_a(NetHandlerPlayServer.java:741) ~[pa.class:?]
at net.minecraft.network.play.client.CPacketPlayerTryUseItemOnBlock.func_148833_a(SourceFile:55) ~[ma.class:?]
at net.minecraft.network.play.client.CPacketPlayerTryUseItemOnBlock.func_148833_a(SourceFile:11) ~[ma.class:?]
at net.minecraft.network.PacketThreadUtil$1.run(SourceFile:13) ~[hv$1.class:?]
at java.util.concurrent.Executors$RunnableAdapter.call(Unknown Source) ~[?:1.8.0_191]
at java.util.concurrent.FutureTask.run(Unknown Source) ~[?:1.8.0_191]
at net.minecraft.util.Util.func_181617_a(SourceFile:46) ~[h.class:?]
... 5 more
I get this spam in the log. Disabling the compatibility fixes the problem.