It is not permissible for an employer to force an employee to work beyond his working hours unless there is a mutual agreement.

Question

It is not permissible for an employer to force an employee to work beyond his working hours unless there is a mutual agreement. Does the same apply to a lunchbreak times stipulated in an employee contract? For example, will an employer be sinful if he gives employees work to do just before they leave for lunch? Or he tells them to come off lunch break to do some work?