Fix: Call to undefined function get allowed block template part areas()

After updating to WordPress version 5.9, you may get a blank white page or a fatal error saying something like:

[26-Jan-2022 15:52:28 UTC] PHP Fatal error: Uncaught Error: Call to undefined function get_allowed_block_template_part_areas() in /home/web/public_html/new/wp-includes/blocks/template-part.php:168

If you only get a white page without seeing anything, you can verify this error by activating the WordPress debug.log.

When this error happens, it means the WordPress automatically went wrong and broke your WordPress installation.

To fix that error, follow the steps below:

  • Download WordPress 5.9 core
  • Extra the zip file
  • Upload only the folders “wp-admin” and “wp-include” via FTP to your website. Overwrite the existing files from that folder.
The next time you update WordPress you can use a website and backup cloning tool like WP STAGING to create a clone of your site and to test updates first on the cloned site before you do it on your production site.

Author: Rene Hermenau

I'm René Hermenau, founder of WP STAGING. I've been building WordPress infrastructure software since 2013 and writing code on GitHub since 2011. My repos live at github.com/rene-hermenau. WP STAGING started as a small developer project solving the same problem I kept hitting on client work: there was no fast, safe way to clone a WordPress site for staging or migration without breaking serialized data, file paths, or media references. Today we are a team of more than 10 people. The free plugin runs on hundreds of thousands of WordPress installations, and the Pro version powers backup, migration, and staging workflows for agencies, hosting platforms, and ecommerce stores. I'm still hands-on with the codebase and technical architecture. Our releases are built as a team, but many of the core architectural decisions are ones I helped design, test, and evolve over the years: how we handle large database exports, how we keep memory usage flat on multi-GB sites, and how we make migrations atomic against partially written tables. "When you touch code, leave it 10% better than before and write a test." If you're stuck on a WP STAGING question, the docs are at wp-staging.com/docs. If you hit a bug, file it on GitHub at github.com/wp-staging. Our team reads everything that lands there.