The phenomenon of reversing the morphological expression of subject-object opposition is well-known in Dutch dialectology, be it that up to now most attention has been devoted to object forms assuming subject function. This article brings to the fore a lesser-known and fairly recent variant of pronominal substitution in West-Flemish dialects where subject forms appear in the object position governed by a preposition. The replacement of oblique forms by subject forms in this syntactic environment appears to be triggered by some diffuseness in the 2nd person morphological system in the S-E of the West-Flemish area. As soon as the tie between semantic case and morphological expression was lifted, the phenomenon quickly spread over the rest of the personal pronoun paradigm, bringing about an adaptation of the linguistic system in the sense that the former case opposition is gradually getting replaced by an opposition between stressed and unstressed forms. The gradual geographic spread over the whole West-Flemish area constitutes an instance of regiolectization.