This paper explores the nexus between the social construction of linguistic borders and the rise of a national identity in post-independence South Sudan. It analyses the indexical functions of Juba Arabic (i.e. árabi juba), an Arabic-based pidgincreole extensively exposed to contact with Sudanese Arabic, its lexifier and former dominant language. By combining insights from descriptive linguistics and discourse analysis, I will argue that, although the metalinguistic representations of Juba Arabic are increasingly driven by the ideological hegemony enacted by the State through its discourse on " indigenous languages " , the construction of linguistic borders between the South Sudanese pidgincreole and its lexifier can also be constrained by cognitively prominent grammatical features.