Resize canvas from windowResize() distorts proportions of 3D objects

Hi everybody,
so when I resize the canvas in this way:

m4.windowResized = function() {
m4.resizeCanvas(m4.windowWidth, m4.windowHeight);
// sphereVertices = pointsOnSphere(etiquetasLength);

the 3D objects on my world get distorted according to the canvas proportions.
This doesn’t happen when I first load the sketch. Is this standard behavior? How can I avoid that?
Thank you for any help