Component selector name wrong

I have a component called header and which creates a special header content inside of the ion-header.
The template code which got generated produced
@Component({
selector: ‘app-header’,

But this component is not rendered as long as it has this name.
When I change the selector to header:
@Component({
selector: ‘header’,

then the content is produced.
I used a dom explorer to verify this behaviour.

Has anyone an idea why it behaves that way.
The prefix “app-” is produced by the template. So it should work with the selector name!

Thanks in Advance!

This was a stupid question.
I just realised that this behaviour change just happened because the news component template sets the prefix “app-” before the component name and my old code just uses the old tag name.
Now i use the tag name with the same selector name and the component gets included without any problems.