According to the so-called 'NP/DP parameter,' languages with articles may project both DP and NP in the nominal domain, while those without can have at most NP with the DP layer missing (Fukui (1988), Chierchia (1998), Bosković (2008), inter alia). Recently, extending this line of reasoning to the clausal domain, Bosković (2010) argues that article-less languages, such as Hindi, Japanese, Korean and Turkish, do not have TP in the clausal architecture. This paper aims to closely examine whether Bosković's claim, referred to as 'TP parameter,' is tenable. We show that careful reconsideration of TP parameter is required since it undergenerates: i.e., there are a number of empirical data in Korean, an article-less language, which it wouldn't be easy to explain unless TP is postulated. The data revealing problems for the parameter include (i) the dependency of licensing negation upon TP in key-ha-la imperatives; (ii) the availability of sentential negation and a verbal predicate in a resulting clause in resultatives; and (iii) the asymmetry between clausal ellipsis and replacement of the pro-form kulehkey.