Skip to main content
warningJava ErrorsAffects: All versions

How to Fix ConcurrentModificationException

Fix ConcurrentModificationException by updating the buggy mod or plugin. This is a threading issue in the mod's code.

Quick Fix

Update the mod or plugin shown in the stack trace. This is a threading bug in the mod's code.

Error Message

java.util.ConcurrentModificationException

How to Fix

1

Update the offending mod or plugin

2

Report the bug to the mod developer

3

If a plugin, check if it is using async tasks incorrectly

4

Reduce server load to make the race condition less likely

Common Causes

  • A mod modifying a list while another thread is iterating it
  • Plugin accessing Bukkit API from async thread
  • Race condition in server tick processing

Diagnostic Steps

  1. Identify the mod from the stack trace
  2. Check if an update is available
  3. If no update, report to the developer
  4. Consider an alternative mod

FAQ

Can I fix this myself?

This is a code bug in the mod. Only the developer can properly fix it. Updating or switching mods is your best option.

Related Errors

Need More Help?