SRB - You may be right. Just found that info referring to the "normal" A320; here's the link
Type Certificate
It states, on page 13, that:
MAXIMUM OPERATING ALTITUDE
39,100 ft (pressure altitude)
39,800 ft (pressure altitude) if modified.
The A319 can really cruise higher than the A320/21 due to a modif (page 36 on the same datasheet no180) that allows a 41,000 ft max op alt.