Failure installing hadoop-hbase on CentOS

Trying to install the CDH3b4 HBase package on CentOS 5.5 (using "yum install hadoop-hbase"), I got the following output:

[...]
Running Transaction
/usr/bin/install: invalid user `hbase'
/usr/bin/install: invalid user `hbase'
error: %pre(hadoop-hbase-0.90.1+8-1.noarch) scriptlet failed, exit status 1
error: install: %pre scriptlet failed (2), skipping hadoop-hbase-0.90.1+8-1
[...]

Looking into the SPEC file of the package, it adds the user with the following command:

/usr/sbin/useradd -c "HBase" -s /sbin/nologin -r -d /var/run/hbase hbase

Executing this gives:

useradd: group hbase exists - if you want to add this user to that group, use -g.

I got it to work like this:

/usr/sbin/useradd -c "HBase" -s /sbin/nologin -r -d /var/run/hbase -g hbase hbase

And then the installation of the package with yum succeeds.