I discuss the status of "mixed category'' genitive prepositions in Hausa. Based on evidence from morphosyntax and extraction, I suggest that the hybrid nature of these prepositional nouns (Wolff 1993) is best understood in terms of decomposition into semantic and morphosyntactic properties: semantically, both true and genitive prepositions are inherent modifiers, selecting their head via the feature MOD (Pollard & Sag 1994). Morphosyntactically, however, genitive prepositions are best treated as nouns, paving the way for a unified analysis of genitive-marked categories in Hausa (nouns, verbal nouns, adjectives). The analysis proposed here is part of a computational HPSG of Hausa.