# OPF-025: list where one value needed, how to fix it

Source: https://epubcc.com/epubcheck/opf-025/ (updated 2026-11-04)

EPUBCheck OPF-025 is an error message: “Property value list "…" is not allowed, only one value must be specified.” A metadata property that takes a single value was given a list of values. EPUBCheck names the list it found, and reading apps would not know which of the values to use.

- Official message (EPUBCheck 5.4.0): Property value list "%1$s" is not allowed, only one value must be specified.
- Default severity: Error

## Typical causes

- Several space-separated values in a property meant to hold one, for example two layout values in one rendition meta element.
- Two values merged into one element when combining metadata from different sources.
- A value with a stray space that splits it in two.

## How to fix it

1. Find the meta element or attribute EPUBCheck points to.
2. Keep a single value.
3. If parts of the book need different values, set them per item in the spine where the property allows it (for example rendition:layout-pre-paginated on one itemref).

## When it's not this

If the single value is malformed rather than doubled, that is OPF-026.

## Sources

- EPUB 3.3, §D.1.2 The property data type: https://www.w3.org/TR/epub-33/#sec-property-datatype (read 2026-11-04)

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