8.4 Data Not Compatible with 9.0.1 Upgrade?

I did an upgrade on my database server this past weekend and the
database fails to start. I checked /var/log/postgresql and found the
reason:

[root(at)slave ~]# ps aux | grep postgres
root 5189 0.0 0.0 8128 956 pts/0 S+ 12:28 0:00 grep postgres

[root(at)slave ~]# /etc/rc.d/postgresql start
:: Starting PostgreSQL

[BUSY] server starting

[DONE]
[root(at)slave ~]# ps aux | grep postgres
root 5205 0.0 0.0 8128 960 pts/0 R+ 12:28 0:00 grep postgres

[root(at)slave ~]# tail -n 50 /var/log/postgresql.log
FATAL: database files are incompatible with server
DETAIL: The data directory was initialized by PostgreSQL version 8.4,
which is not compatible with this version 9.0.1.
FATAL: database files are incompatible with server
DETAIL: The data directory was initialized by PostgreSQL version 8.4,
which is not compatible with this version 9.0.1.
FATAL: database files are incompatible with server
DETAIL: The data directory was initialized by PostgreSQL version 8.4,
which is not compatible with this version 9.0.1.

Does anyone know if this is a issue with PostgreSQL or with the way
Arch Linux packages the upgrade?