# EPUBCheck PKG-001: Validating the EPUB against version …

Source: https://epublab.com/epubcheck/pkg-001/ (updated 2026-11-03)

EPUBCheck PKG-001 is a warning message: “Validating the EPUB against version … but detected version ….” EPUBCheck was told to validate one EPUB version but the package document declares another.

- Official message (EPUBCheck 5.4.0): Validating the EPUB against version %1$s but detected version %2$s.
- Default severity: Warning

## Typical causes

- EPUBCheck was run with -v 2.0 or -v 3.0 and the file's package element has a different version attribute.

## How to fix it

- Run EPUBCheck without -v on a packaged .epub file: it reads the version from the package document.
- If the version attribute itself is wrong, set it to the version the content really follows: version="3.0" for EPUB 3.

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