This article investigates the effect of the unique contact situation between users of Afrikaans and the native variety of South African English (SAfE) on the propagation of the distinctive macro- and microsemantic properties of SAfE must. This modal verb has gradually become less face-threatening in SAfE over the course of the 19th and 20th centuries, conveying a median (weaker) degree of force just as frequently as a higher degree of force by the 1990s, which has in turn led to its increased use in deontic (personal) contexts (Wasserman 2014).These semantic changes differ greatly from the changes that occurred in other native varieties of English in the world (cf. Leech et al. 2009). The primary question this article seeks to answer is whether these distinctive properties of SAfE must have developed due to the contact that this variety has maintained with Afrikaans over the course of the 19th and 20th centuries. The discussion firstly provides extralinguistic motivation, and secondly linguistic (synchronic and diachronic) motivation based on corpus data, in support of the influence of Afrikaans moet on SAfE must. The extralinguistic discussion explores the complex sociopolitical relationship between users of Afrikaans and SAfE, along with issues of race and identity, and bilingualism and the education system. It is argued that the periods of fluctuating enmity and friendliness that the English and Afrikaans communities have maintained, as well as the somewhat forced contact situation instituted by racial segregation during the latter part of the 20th century, has allowed these communities to interact in such a way as to affect the mutual influence of their languages, even without the alignment of their identities. The social trend of Afrikaans-speaking teachers instructing English-speaking children during the 20th century has further contributed to the influence of Afrikaans on SAfE. The linguistic discussion on the other hand investigates if and how SAfE must fulfils the linguistic criteria for contact-induced change. This part of the discussion firstly emphasises the similarities between moet and must on grammatical and semantic levels, seeing that Afrikaans and English are close West-Germanic relatives. Special attention is devoted to a comparison between the levels of grammaticalisation of moet and must, especially regarding their respective negative forms moenie and mustn't. Both the synchronic and diachronic quantitative results clearly show the "pull" of Afrikaans moet on SAfE must in terms of usage frequency, which is also confirmed by the diachronic qualitative results. The diachronic qualitative analysis reveals a move toward the expression of very similar macro- and micro-meanings by Afrikaans moet and SAfE must in the written register during the course of the 1910's-1950's to the 1990's-2010's, especially in favour of the expression of a median-degree of obligation via an objective deontic source. SAfE must therefore does follow an Afrikaans-like semantic pattern, confirming the influence of Afrikaans on this English variety. The close, yet complex, relationship that SAfE and Afrikaans have maintained over the course of two centuries is not truly matched anywhere else in the world, and has indeed given rise to a usage pattern of must that is unique among other English varieties. [ABSTRACT FROM AUTHOR]