Database migration fails from v1.0.2 to v1.1-beta1

After migrating from Sonar v1.0.2 to v1.1-beta1 like explained in the docs, I run the Sonar plugin ("mvn org.codehaus.sonar:sonar-maven-plugin:1.1-beta1:sonar") and received the following exception:

[ERROR] Cannot execute the command org.codehaus.sonar:sonar-core-maven-plugin:1.1-beta1:collect
org.apache.maven.lifecycle.LifecycleExecutionException: DB model exception occured
[...]
Caused by: org.hibernate.HibernateException: Wrong column type: created_at, expected: timestamp

Reason is probably that the "snapshots" and "snapshot_groups" tables have a column "created_at" of type "date". After changing these two columns (see SQL statement below) everything worked fine...

alter table snapshot_groups modify created_at timestamp(6);
alter table snapshots modify created_at timestamp(6);

(note that I am running Sonar on a Oracle 10g database)