The text selection in Firefox is still working after disabling it from CSS

The text selection in Firefox is still working after disabling it from CSS

I am using the CSS rule:
.noselect {
-webkit-touch-callout: none;
-webkit-user-select: none;
-khtml-user-select: none;
-moz-user-select: moz-none;
-ms-user-select: none;
user-select: none;
}
This disables the selection of a div like the one below in Chrome but not
in Firefox:
<div class="noselect">
<span>This text cannot be selected</span>
</div>
I have the latest browser versions. A sample can be found in this jsFiddle.
What is different in Firefox? How can I disable the selection there?