Abstract This paper analyzes Differential Object Marking in P’orhépecha, which involves split case and fluid case alternations. Although this system is sensitive to Animacy and Definiteness, I will show that prominence on these scales does not account for the distribution of flagging. In fact, in P’orhépecha, the expected prominence effects of these scales are overridden by certain grammatical properties of the NPs, which explains the obligatory vs. forbidden flagging. The fluid pattern is of special interest, since even though there is evidence that flagging is used as a device to codify definiteness/specificity, higher and lower ranked objects on the definiteness scale may be (un)flagged. This peculiar behavior is explained by two facts: (a) definite/specific descriptions may, and in some instances must, be unflagged when the context of use guarantees the intended referential interpretation of the NP; and (b) lower ranked objects may be flagged only when their referents exhibit discourse salience.