Since Badiou equates ontology with Mathematics, if both philosophers are to be taken verbatim, there's a triple equivalence to consider: ontology = Mathematics = language.
See the original text into the Tractatus:
5.6 The limits of my language mean the limits of my world.
This must be read in the context of W's view about the "un-sayable" :
5.61 We cannot think what we cannot think; so what we cannot think we cannot say either.
We understand the world through language, that mirrors facts, and there is no way to "step outside" language to compare the language with the world.
Having said that, for Wittgenstein mathematics is not equal to language.