Failed WordPress Upgrade

The error message:

Fatal error: Call to undefined function update_core()

The Cause:

You don’t have enough disk space on your hosting account anymore.

The Fix:

Pick one:

  • Ask your web host to bump up your allowed disk space
  • Delete unneeded files on your account
  • Move to a new web host


I never ran into this problem before, but during an update to WordPress 3.4, the error kept appearing every time the upgrade script tried to unpack the downloaded zip file from  It would be helpful if they included a message about it to let you know you may be out of space, but at least you can Google the error and find this page now 🙂

About Will Chatham

Will Chatham is the Security Assessment Engineer for Arbor Networks. Since Netscape 2.0, he has worked in a wide array of environments including non-profit, corporate, small business, and government. He started as a web developer, moved into Linux system administration, and ultimately found his place as a security professional. Having most recently conquered the OSCP certification, Will continues to hack his way into various things in an effort to make them more secure.
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