In mathematics, it is common practice to have several constructions for the same objects. The mathematicians will identify them modulo isomorphism and will not worry later on which construction they use, as theorems proved for one will be valid for all. When working with proof assistants, it is also common to see several data-types representing the same objects. This work aims at making the use of several isomorphic constructions as simple and as transparent as it can be done informally in math. This requires inferring automatically the missing proof-steps. We are conceiving an algorithm to do so and implementing it as a plugin for Coq.