Colloquial Singapore English has a novel conditional construction in which the conditional clause is not marked morphosyntactically, and must precede the consequent clause. We show that Singapore English, like Chinese, the main substrate language, is topic prominent, and the novel conditional construction is a direct consequence of this new typological status. We analyze the unmarked conditional clause as topic, a basic syntactic position in topic prominent languages. Our analysis shows that substrate influence is systemic: the entire cluster of properties associated with topic prominence is transferred from Chinese to Singapore English.