# EPUBCheck PKG-005: The mimetype file has an extra field of…

Source: https://epublab.com/epubcheck/pkg-005/ (updated 2026-11-03)

EPUBCheck PKG-005 is an error message: “The mimetype file has an extra field of length …. The use of the extra field feature of the ZIP format is not permitted for the mimetype file.” The mimetype entry in the ZIP carries an "extra field", which the EPUB container rules forbid for that one file.

- Official message (EPUBCheck 5.4.0): The mimetype file has an extra field of length %1$s. The use of the extra field feature of the ZIP format is not permitted for the mimetype file.
- Default severity: Error

## Typical causes

- ZIP tools that add extended timestamps or file attributes to every entry by default, as many desktop compressors do.

## How to fix it

- Zip the mimetype file without extra attributes. With Info-ZIP the -X option leaves them out: Rebuild the archive with the mimetype file first and stored uncompressed, for example from the folder that contains the book: zip -X0 book.epub mimetype and then zip -rX9 book.epub META-INF OEBPS (use your own folder names).

Message text and severity: EPUBCheck (W3C, BSD-3-Clause). Explanation: EPUBLab.