Fatal error: Call to undefined function wp_initial_constants

Updated and now site is down.

I logged in to wp-admin, went to the updates page.

“An updated version of WordPress is available.

You can update to WordPress 3.7.1 automatically or download the package and install it manually:”

I clicked the “Update Now” button and the site stopped working.

“Fatal error: Call to undefined function wp_initial_constants() in /*****/*****/public_html/wp-settings.php on line 26”

I would appreciate any tips on getting the site up and running again.

Is there an edit I can make to wp-settings.php to make the site work again?

Many thanks for any help.

Rob