Relationship required not working for one-to-many

I defined a bidirectional relationship with attributes as followed:

– Options: Required
– Selection type: “Multiple Select”
– Format: “Autocomplete”
– Add allow new: “Yes”

If I fill out other custom fields but don’t define a relationship for the custom relationship field the pod’s custom fields will not be saved because the empty relationship.

Why doesn’t the “required” option work? I would expect that I cannot safe the pod until at least one relationship is defined and the relationship field should be displayed in red or did I do something wrong?

Any help would be greatly appreciate
Albrecht