Geez

-u/-o, -hu - his (genitive pronominal suffix, 3 masc. sg.) (CDG 213, Bulakh–Kogan 2013b:101)

The form of the possessive suffix with nouns in nominative case is -u, while the allomorph used with nouns in accusative is -o. -hu is the allomorph used with forms ending in a vowel. See Bulakh–Kogan 2013b:103, 105.

PS
*-šū̆ - his; him (genitive and accusative pronominal suffix, 3 masc. sg.) (Kogan 2009:69)
The shift *š- > h is distributed between languages the same way as in the realm of independent pronouns of the 3rd person.