This study aims at comparing the structures from French and Spanish respectively Comme dit le proverbe / Como dice el refrán as far as the insertion of the neutral object pronoun le / lo is concerned. According to a common view, such an insertion would be totally free in French (Comme le dit le proverbe) and completely impossible in Spanish (*Como lo dice el refrán). A more careful examination shows that in fact the insertion can happen to be obligatory in French (Comme (l + *ø) autorise la loi) and perfectly feasible in Spanish (Margarita vendrá mañana, como te (ø + lo) prometieron sus padres). It will be shown that this pronominal insertion is in fact constrained in both languages by specific rules governing the polyphonic/evidential structure.