When an object from a class Foo is associated with a Bar object, we don't always want to have the association. So when in the view we've got a select which shows all Bar instances, an empty option would be good to. Example use case from Fred Janon: I have an "Shift" domain class that references an "Officer" domain class. An "Officer" can be optional assigned to a "Shift". The user can change the date/time of the "Shift" and at some point assign an "Officer" to the shift. By default Grails builds an "Edit" view for the "Shift" with a "Select" referencing the "Officer" list. The problem is that the "Select" doesn't have an empty entry for the "Officer". Even if the user wants to change only the time of the shift, the first officer will be selected by default and saved. Is there a way to make the "Officer" field optional in the "Edit Shift" view? This is the code generate by Grails: <g:select optionKey="id" from="${[''] + Officer.list()}" name="officer.id" value="${shift?.officer?.id}"></g:select> I added an empty entry in the list, it shows correctly in the HTML page, but then Hibernate generates an exception when I save the edited "Shift" <g:select optionKey="id" from="${[''] + Officer.list()}" name="officer.id" value="${shift?.officer?.id}"></g:select> Any suggestion to do this cleanly?