Session File Store: inaccessible directory "/tmp" (source)

View source for Session File Store: inaccessible directory "/tmp"

Installed wacko, all successful until finally got error message: 
SessionFileStore: inaccessible directory "/tmp" and blocked ("rien ne va plus") 

Tried/checked
- manually make new directory tmp + releasing rights
- opened config.php and looks fine 

Installation: 	
- 'wacko_version' => '5.5.8',
- locally, on xampp windows ###### ApacheFriends XAMPP Version 7.2.4 ######

What did I do wrong? Tnx in advance!