Cannot parse double values from XML element

When I set an attribute like this:

QDomElement element = doc.createElement("foo");
element.setAttribute("x", 666.666);

This results in the value being "666,666".

Now, if I parse the element like this:

double x = element.attribute("x", "0").toDouble();

...it results in 0.

I don't find it logical that the element cannot parse a double value that was set by itself. If this is "excepted behavior" then how parsing a double should be handled..?