In this paper we examine the use of Guarani affixes and clitics in colloquial Paraguayan Spanish. We depart from the traditional view of these as "borrowings," and instead explore the idea that these phenomena can be integrated within Muysken's (2000, 2013, 2014) typology of code-mixing. We claim that most of these uses may stem from a strategy of backflagging that bilingual speakers employ to mark their use of a (historical, colonial) L2 (Spanish) with elements from the original community L1 (Guarani). In so doing, however, we identify some problematic areas in applying Muysken's model to these data. We conclude by showing how this perspective shift in the analysis of Guarani-Spanish contact phenomena can both increase our understanding of this particular contact situation, as well as of code-mixing typology.