conditional processing for title page

Hi guys,

I am using conditional processing for a documentation of 2 product variants.
That's working great, but I would like the title & subtitle to be a different... I tried it as shown below, but get an error when rendering the PDF.
Any idea if there is a way to achieve this?

ifdef::product1[]
**Setup Guide 1**
=================
Subtitle 1
v{version}
:imagesdir: ./images/setup
:toc: left
:toclevels: 4
:guidename: Setup Guide 1
:releaseyear: 2020
:compat-mode!:
endif::solo[]

ifndef::product1[]
**Setup Guide 2**
=================
Subtitle2
v{version}
:imagesdir: ./images/setup
:toc: left
:toclevels: 4
:guidename: Setup Guide 2
:releaseyear: 2020
:compat-mode!:
endif::solo[]

Thanks!
Chris