PHP Fatal error: Call to undefined function flexslider_optionset_create() in flexslider/flexslider.flexslider_default_preset.inc on line 14

drush en flexslider_views
The following extensions will be enabled: flexslider_views, flexslider
Do you really want to continue? (y/n): y
PHP Fatal error: Call to undefined function flexslider_optionset_create() in flexslider/flexslider.flexslider_default_preset.inc on line 14