How to call an async function inside then() in CasperJS?

Question

I have a scenario in which I need to call APIs during a Casper test. In order to call these APIs, I'm thinking of using then().

The problem is that Casper doesn't wait whatever I pass to then(), even if I return a Promise like this:

casper.then(function() {
    return new Promise(function(f, r) {
       setTimeout(function() {
           console.log('waited 10 secs');
           f();
       }, 10000)
});});

How can I make Casper wait inside the function I pass to then()?