List Values default to label 1 when list value changes

Hi All,

I am using two list boxes on changing the list box one list box two value changes

both of the list box i kept default selected value as label one

by change in the list box one it will change in list box 2 with default selection label 1

now had added header value  to the list box 1 and made default  as header value

now change in value in the list box 1 is changing the list box 2 but the selection in list box 2  is empty

how to resolve it

Please advise

Thanks

Krishna M