Radio button checked attribute not updating on user action

Radio button checked attribute not updating on user action

I am trying to monitor the change on a radio group.
I am using topcoat with the following HTML :
<ul class="topcoat-list">
<li class="topcoat-list__item">
<label class="topcoat-radio-button__label">
<input type="radio" name="topcoat" value="1" checked="checked">
<div class="topcoat-radio-button"></div>
Test1
</label>
</li>
<li class="topcoat-list__item">
<label class="topcoat-radio-button__label">
<input type="radio" name="topcoat" value="2">
<div class="topcoat-radio-button"></div>
Test2
</label>
</li>
<li class="topcoat-list__item">
<label class="topcoat-radio-button__label">
<input type="radio" name="topcoat" value="3">
<div class="topcoat-radio-button"></div>
Test3
</label>
</li>
</ul>
For a reason I don't quite get, the checked attribute does not get updated
when the use selects another radio button...
I would like to be able to monitor the change with javascript, but right
now, I can't get the value of the radio group...