Apply CSS style to an existing link

I created a custom style for styles drop down list:

<Style name="LinkCSS" element="A">
<Attribute name="class" value="LinkCSS" />
</Style >

When I select some text (step 1), apply a link with the toolbar function (step 2) and apply my LinkCSS class (step 3), no "class" attribute is inserted.

step 1: hello world!
step 2: hello <a href="xxxxxxx">world</a>!
step 3: hello <a href="xxxxxxx" class="LinkCSS">world</a>!

Is this a bug or a normal behaviour?

My editor version: FCKeditor 2.6.4