Exceptions thrown in Promise.then()'s onRejected not handled properly

I'm facing a bug in Qt's Promise implementation. Exceptions thrown from the second argument of Promise.prototype.then()'s argument aren't propagated to the following .catch() statement.

I have a simple test case:

Promise.reject("Some error")
.then(
     o => console.log("Never reached"),
     err => {
         console.log("Rethrowing err");
         throw err;
     }   
)   
.catch(err => {
    console.error("The error is: " + err);
}); 

This is what it should print:

Rethrowing err
The error is: Some error

and it does so under Node.js and Mozilla Firefox.

However, it only prints the first line under Qt, because the .catch() part isn't run at all.