Immunization - PV or MV?

Hello,

I was slightly thrown by a MM practice question on immunizing. My understanding was you wanted MV of assets greater or equal to liabilities as one of the criteria.

One of MMs practice questions on a Mock has you deciding based on the PV and not market value of assets and liabilities. You had to discount an asset and liability that matured at the same value at the same time but that were priced with different rates and so you discount both back to PV and use that as guiding criteria in which is appropriate to immunize.

Is this correct, it is PV of asset > than PV liabilities and not MV ?