<jats:p>Structuralists and generativists have insisted for a long time that the elements and structures one language could borrow from another are constrained by typological compatibility, naturalness, and other factors (cf. Thomason and Kaufman 1988: 13–34). Such constraints are still thought to apply to structural interference, or pattern replication in the terms of Matras and Sakel (2007), and the often concomitant contact-induced grammaticalisation of non-native structures.</jats:p><jats:p>This paper suggests that <jats:italic>a priori</jats:italic> there are no typological constraints against pattern replication in general. It is proposed that typological differences between model and replica pattern are only of relevance during the grammaticalisation and maintenance of such patterns in the replica language; in other words, typological constraints do not apply at the stage of pattern replication. It will be argued that typology, in the form of system pressure, interacts with pattern frequency and socio-historical factors, which together determine retention, adaptation, or loss of a replicated pattern.</jats:p><jats:p>This argument is illustrated on the basis of three short studies of partial alignment change in Old Aramaic, Classical Armenian, and North-Eastern Neo-Aramaic, all of which have been in contact with Iranian languages for extended periods. In each case, Iranian ergative alignment patterns have been replicated, adapted, grammaticalised to varying degrees, and finally ousted in favour of nominative-accusative alignment. The loss of the replica pattern in each case is shown to be dependent on both typology, extent of bilingualism, and pattern frequency.</jats:p>