Restricted course Units are visible without completing the pre-requisite Unit (bug)

Course Units have a checkbox saying: [check box] "User needs to complete current unit in order to access the next one"

However this is not restricting permission to the units for a student.

On the demo I set up here...

http://course.simplecsr.com/courses/test-course/

All the units should be restricted however as soon as you sign up any unit can be completed in any order.

(This should be quick to replicate by creating a new course adding 2 units with the checkbox ticked. )

Thanks
Chris