Dojo: dynamically select checkbox

I work with Dojo 1.11. Currently I'm having a ridicilously simple issue that I cannot solve. I have a dijit/form/CheckBox checkbox declared in my template like this:

<input name="realizationProcedureLock" id="realizationProcedure_lock_${id}" value="" data-dojo-type="dijit/form/CheckBox" data-dojo-attach-point="realizationProcedureLock" data-dojo-props="checked: false"/>

In my js template I want to uncheck it:

 on(this.importMonth, 'change', function () {
...
// uncheck the cb when changing months
this.realizationProcedureLock.checked = false;
...
}

This does not work although there is a checked property on this.realizationProcedureLock which changes when set. When this property is false and the checkbox is selected, hovering over the checkbox unselects it...

What is wrong here?