Subpart assignment across sheet instances

[gxti]

Is there some trick to getting Altium to assign subparts across multiple instances of a sheet symbol? For example if I've got a subsheet with a 1/4 op-amp, and then have 4 instances of that sheet, it uses the "A" subpart for every instance which means I get 4 quad op-amps with only the "A" subpart used, instead of 1 quad op-amp with each subpart going to one sheet. On the other hand, if I have 4 unique sheets the renumbering spreads the subparts across all four sheets like it should. It just doesn't know how to spread them across multiple instances of the same sheet.