AS3 embedding fonts and TextFormat

A few days ago I had a problem with using a font from the library (which is in the .fla) in a class file (which is an .as).
If you have created a font in your .fla by Library>New>New Font, use it's name like below in the class file to use it:

var format3:TextFormat = new TextFormat();
format3.font = "BM mini";
format3.color = 0x6AB779;
format3.size = 20;
format3.bold = true;
format3.align = TextFormatAlign.LEFT;

Now, this is the usual TextFormat use, to use this new format on a TextField object, I thought I would use "defaultTextFormat = format" as usual. Wrong. defaultTextFormat did not work, however, setTextFormat(format) works:

myTextField.setTextFormat(format3);