Syntax error for a JS function with default parameters

Qt Creator gives me a syntax error for the following code:

function someFunction(someVar, anotherVar = false) // "=" is underlined and "Syntax error" is shown
{
    if (anotherVar === true) { console.log(someVar); }
}

I might be wrong, but default parameters for JS functions were added in ECMAScript 6, and Qt now supports ECMAScript 7, so it should not be a syntax error.