I have tested this and I could indeed reproduce it.
This seems to be either an issue or a limitation to our support for the MessageBox custom action.
I have forwarded this to our development team for a fix/improvement in the future.
Until then, as a workaround, you can try to generate the message box through another custom action. For instance, you can use the "Execute inline script code"
to create the message box using VBS
, as it follows:
Code: Select all
prop = Session.Property("MyProp")
is the property that you defined in the "Install Parameters"