Clicking an optgroup triggers n change events, where n is the amount of options that are selected/deselected

[Lxxrxns]

I have a listener for a change in a multiselect box, but when I click an optgroup, this triggers n changes, where n is the amount of options in that group. This results in unwanted behaviour.

Can you think of a work-around to consider clicking an optgroup as a single change?