Upgrade issue: Textile class missing

After an upgrade to the current release of Perch, we are running into an issue when saving fields that are actually using the Blog and Event add-ons with ckeditor.

Fatal error: Class ‘Textile’ not found in …/addons/apps/perch_events/PerchEvents_Events.class.php on line 460

— this is without Textile being referenced anywhere in the template.

Any ideas?