IO Error: cannot assign "builtin" because "plugin" is null

Started by luislewington on

Topic category: Troubleshooting, bugs, and solutions

Joined Mar 2025
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IO Error: cannot assign "builtin" because "plugin" is null

So I recently got into modding using MCreator, and I've been hoping to try loading the fabric generator addon. Unfortunately, despite following all the steps for downloading and adding an addon to MCreator, the addon keeps failing to load. The error message I get says "IO Error: cannot assign "builtin" because "plugin" is null. I am making a post about this because I have found a few reddit posts, and even a forum post here talking about this, but no proper solution is provided.

You must not install plugin…
Tue, 04/01/2025 - 16:21

You must not install plugin into plugins of install dir, but in <user home>/.mcreator/plugins

otherwise it will break the software

Joined Oct 2026
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Is this the location that it…
Sun, 10/04/2026 - 02:17

Is this the location that it gets automatically added to if I were to go into preferences in the manage plugins section? Because I am still experiencing this problem 

Yes, preferences will put…
Mon, 10/05/2026 - 14:33

Yes, preferences will put into right location. If you still have this problem, get in touch with the plugin author