# EPUBCheck OPF-007: Re-declaration of reserved prefix …

Source: https://epublab.com/epubcheck/opf-007/ (updated 2026-11-03)

EPUBCheck OPF-007 is a warning message: “Re-declaration of reserved prefix "…".” The package document re-declares one of EPUB's reserved prefixes.

- Official message (EPUBCheck 5.4.0): Re-declaration of reserved prefix "%1$s".
- Default severity: Warning

## Typical causes

- Copying a prefix attribute that includes mappings for reserved prefixes such as dcterms or rendition.
- Hand-edited or tool-generated package documents that write the prefix attribute with the wrong separators.

## How to fix it

- The prefix attribute on the package element maps short prefixes to vocabulary URIs, as space-separated pairs like prefix="ibooks: http://vocabulary.itunes.apple.com/rdf/ibooks/vocabulary-extensions-1.0/". Remove the mapping for the reserved prefix from the attribute.
- Reserved prefixes such as dcterms, rendition and schema need no declaration at all.

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