> For the complete documentation index, see [llms.txt](https://itemsadder.devs.beer/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://itemsadder.devs.beer/japanese/old/old-guides/internal-exception.md).

# Internal Exception

## First fix

Try to update to the latest ProtocolLib and if you use ViaVersion also update it.

## Second fix (if required)

`Internal Exception: io.netty.handler.codec.DecoderException: java.lang.IndexOutOfBoundsException: index: 5, length: 13632 (expected: range(0,30))`

![](/files/6hlbpPU15bLiZBYy4d3q)

Open `config.yml` of **ItemsAdder** and change this value to `false`: `optimized-packets: false`

{% code title="config.yml" %}

```yaml
  custom-entitites:
    optimized-packets: false
```

{% endcode %}