# E4049

Compiler diagnostic name: `pkg_magic_mismatch`.

Magic number mismatch for the package file.

This means your local build files are corrupted or outdated. First try
update/reinstall your MoonBit installation as in our [Download
Page](https://www.moonbitlang.com/download/). Then try to run `moon clean`
or remove the `target` directory manually and build again. If the error
persists, please submit a bug report here:

<https://github.com/moonbitlang/moonbit-docs/issues/new?labels=bug,ICE>

This package-loading diagnostic has no checked source example because producing
it depends on stale or incompatible internal build artifacts rather than
ordinary source code.