Are class names in CSS selectors case sensitive?

I keep reading everywhere that CSS is not case sensitive, but I have this selector

.holiday-type.Selfcatering

which when I use in my HTML, like this, gets picked up

<div class="holiday-type Selfcatering">

If I change the above selector like this

.holiday-type.SelfCatering

Then the style does not get picked up.

Someone is telling lies.