We present a pilot study investigating a possible interaction between the Northern Subject Rule (NSR) and negative declarative do-support in Scots during the 16th to 18th century; Scots, a West-Germanic variety traditionally spoken in lowland Scotland, fell under increasing influence from English during this time period, the same period in which we also see Scots do-support emerging. The NSR is a subject-verb (s-v) agreement system in the present tense, which requires structural adjacency and specific subject types (1sg or any plural pronoun, 'NSR subjects') in order for s-v agreement to take place, as analysed by de Haas (2011). With evidence from a present-day Scots variety, Buckie Scots, of negative declarative do-support appearing variably with NSR subjects (Smith 2000), we ask whether there is a subject type constraint on the rise of do-support in the history of Scots: We predict that there would be lower frequencies of do-support with NSR subjects (i.e. the Buckie pattern), and investigate our prediction using automatically parsed data from the Helsinki Corpus of Scottish Correspondence (1540-1750; Meurman-Solin and VARIENG 2017). We do not find the expected correlation of do-support and NSR subjects in our data, and we discuss the status of the negator and the adjacency constraint on the NSR as factors affecting these results, which we will consider further in future study.