# EPUBCheck OPF-026: Found malformed property value: …

Source: https://epublab.com/epubcheck/opf-026/ (updated 2026-11-03)

EPUBCheck OPF-026 is an error message: “Found malformed property value: "…".” A property value is malformed, for example a prefix with nothing after the colon.

- Official message (EPUBCheck 5.4.0): Found malformed property value: "%1$s".
- Default severity: Error

## Typical causes

- Values such as "rendition:" or values with spaces or characters a property name cannot have.

## How to fix it

- Write the property as prefix:name (or a plain name from the default vocabulary) with nothing missing.

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