Will saving and re-publishing update the physics?

So the latest update states there's a new physics engine, with performance enhancements. Will opening my project and re-saving it be enough to update to the new physics engine, or do I have to re-apply all the physics behaviors to the relevant objects? Wanted to make sure, as unfortunately it may not be worth the bother if it's the latter case.

it will add any fixes made. to be sure your using asm.js engine just go to your Project setting and look at the Physics engine Setting and ensure it's set to Box2D asm.js

Lovely, thanks for the help.