It is usual specifically in Bantu languages for the prohibitive to be molded by a construction consisting of a cessative verb in collocation with a non-finite verb. This is also the case in Manda, a Southern Tanzanian Bantu language. In Manda, a negative imperative is expressed by the auxiliary -kotok-, with the (lexical) meaning ‘leave (off), stop’, operating on an infinitive full verb. This study shows that the functional and formal variation of this construction reflects a historical and ongoing process of grammaticalization along the verb-to-affix cline, asserting that -kotok- is transforming into a more general non-main negation marker.