Members area downloading file on front end

I'm getting a fatal error whenever trying to download a document which has been uploaded to the members area.

Fatal error: Call to undefined function mime_content_type() in /SITEPATH/admin/addons/apps/perch_members/runtime.php on line 297

Filepath and webpath are correct in the buckets.php file.

The document's are being uploaded to the secure folder area without any issue it's just whenever they are being downloaded on the frontend.

Any ideas what might be causing this?

Thanks