Turkic languages have been argued to require a configurational analysis for the distribution of structural accusative and dative, but it is debated whether this should extend to nominative and genitive. This paper argues that a configurational analysis can be upheld for nominative/genitive alternations in differential subject marking (DSM) constructions by analyzing argument clauses, but not adjunct clauses, as complex NPs with an optionally null head noun. This head noun creates the nominal case assignment domain required for the assignment of genitive case.