In my case the solution was the following code:
<CheckBox
IsChecked="{Binding IsSelected, RelativeSource={RelativeSource TemplatedParent}}"
Padding="{TemplateBinding Padding}"
HorizontalContentAlignment="{TemplateBinding HorizontalContentAlignment}"
VerticalAlignment="{TemplateBinding VerticalContentAlignment}"
ContentTemplateSelector="{TemplateBinding ContentTemplateSelector}"
Content="{TemplateBinding Content}"
ContentTemplate="{TemplateBinding ContentTemplate}"/>