Checking for inclusion in a new list

Hallo. I'm using the formula below to compare a new list with items in an old list. The formula returns X when there is something that is not included in the old list. However, it also returns X's when the rows are blank in the new list (and there are many blank rows). Can I modify the formula or eliminate all blank rows? I'd prefer to modify the formula but either or. Obrigadoooooooooo

=IF(ISNA(MATCH(A2,SheetA!$A$2:$A$11000,0)),"X","")