Change the material of a lightmapped object

I'm changing the color property of a material of a lightmapped object on the fly using this code:

 MeshRenderer mesh = gameObject.GetComponent<MeshRenderer>();
 mesh.material.color = new Color(255, 255, 255);

The problem is that when I do it the color does change, as it's supposed to do, but the object lose his lightmap. Anybody knows why it happen and if there's any workaround to solve it?

PS: If I change the color property by the inspector panel instead of code, it works.