Udi is a Nakh-Daghestanian (Lezgic) language spoken in northern Azerbaijan, which has undergone many contact-induced changes due to the influence of unrelated languages of the eastern Caucasus (Indo-European, Turkic). A recent change is the borrowing of the conditional enclitic =sa from Azerbaijani (Turkic). In Udi, this marker can combine with finite indicative tenses, resulting in a series of derived ‘realis’ conditional mood forms. The clitic is also used to create an indefiniteness marker, which derives indefinite pronouns from interrogative ones. Prior to the borrowing of the Azerbaijani morpheme there was no comparable marker in Udi available to fulfil these functions, while other Lezgic languages employ their own native grammatical means for the same functions (conditional clitics or auxiliaries). The acquisition of the borrowed clitic has thus made Udi more and not less structurally isomorphic with respect to the other languages of the Lezgic branch. This paper develops a description of functions related to the domain of conditional mood on various stages of the history of Udi, and suggests a diachronic scenario for the borrowing of the Azerbaijani marker =sa.