Ion-select doesn't reset when setting model to undefined

Ion-select should just show blank and not show anything selected when i set the model to undefined, however even if the model is set to undefined the previous value still show, and the select when opened shows selected when it should not.

Can you provide a demo of this?

http://codepen.io/tlancina/pen/EPBdVE/

Ok i had 2 select and the second one’s options were filtered by a value from the first, i fix this setting the 2º select model to -1 instead of undefined.