Common Crash Issues [PLEASE READ FIRST]


There a few well-known crashes that happen with SpongeForge and some modpacks at present, that can easily be fixed. If your server is crashing upon startup, please check if a part of your server log matches the examples below - and if so, try the suggested fixes.

In general, if you are having issues setting up a sponge server, or think you may have found a bug, search this category and check that the problem hasn’t already been reported. If it’s still unique, you may post a new topic here in the Sponge Support section, or follow our bug reporting guidelines for GitHub (

Well Known Issues


If you have the mod FoamFix, you may get an exception in your logs that looks like this:

Description: Exception in server tick loop
java.lang.NoClassDefFoundError: net/minecraft/world/chunk/BlockStateContainer

This is because both SpongeForge and FoamFix add some optimizations that do not work with each other! This is easily remedied by disabling the following settings in the config/foamfix.cfg file:


Old Mixin

If your server is crashing early in the startup process, or you see an exception complaining about “failing to apply mixins”, the issue may be that a mod is loading an outdated Mixin version before Sponge. Mods load in alphabetical order, so this can usually be fixed by renaming the SpongeForge jar file, so that it loads before the problematic mod. That is, e.g. rename spongeforge-1.12.2-2768-7.1.6-RC3616.jar to _aspongeforge-1.12.2-2768-7.1.6-RC3616.jar.

None of the Above

If none of the aforementioned fixes solve your issue, then we encourage you to post in this category and share the problem. Please try to provide as much useful information as you can, allow time for people to respond - all our staff are volunteers. Also note that often we can’t really help without seeing log files. When asking for help, please include a link to your the server.log/debug.log file, uploaded to one of the following sites (or equivalent):

Other useful information includes the versions of SpongeForge, Forge, Java, OS, and whether you have recently updated any mods or plugins, or if the server was forcibly shut down recently. It also helps to explain what fixes you have already tried, and what your thoughts are, because we can use your help in finding the bugs so they can be fixed…

Server crashing-- Please help?
Sponge crash when picking up an item
Problem with server