[TYPO3] Alias appears to bypass 404 handling

[David C. Evans]

Hi,
 
I have a setup using SimulateStaticDocs and mod_rewrite that is working
well except for one thing:
 
If a user goes to '123.html' and '123' is not a valid ID in the
database, the 404 handling is engaged, as it should be. However, if a
user goes to 'page.html' and 'page' is not an alias in the database,
Typo3 serves the root page back. I would like to configure it to serve
back the 404 page if an alias does not exist, but can't find out how to
do this.
 
Thanks in advance for your help,
 
David Evans