IF(ISBlank with Vlookup

=IF(ISBLANK(Q19),"-",VLOOKUP('ITEM ADD-CHG Form'!Z19,Brand_V,2,FALSE))

If cell Q19 is blank, return a dash
If cell Q19 is not blank, run a Vlookup on cell Z19 against named range Brand_V and return value of column 2

I'm getting a dash, when cell Q19 is *not* blank

If I run the VLookup string
=VLOOKUP('ITEM ADD-CHG Form'!Z20,Brand_V,2,FALSE)
I get the proper answer. When I insert the IF(ISBLANK statement, I'm getting the dash.