java.sql.SQLException: Unexpected token: JOIN

I get every 5 minutes this kind exception in the error log (openfire_2015-03-23.deb, HSQL Database):

2015.03.24 16:04:47 org.jivesoftware.openfire.pubsub.PubSubPersistenceManager - Unexpected token: JOIN in statement [DELETE FROM ofPubsubItem LEFT JOIN (SELECT id FROM ofPubsubItem WHERE serviceID=? AND nodeID=? ORDER BY creationDate DESC LIMIT ?) AS noDelete ON ofPubsubItem.id = noDelete.id WHERE noDelete.id IS NULL AND ofPubsubItem.serviceID = ? AND nodeID = ?]

java.sql.SQLException: Unexpected token: JOIN in statement [DELETE FROM ofPubsubItem LEFT JOIN (SELECT id FROM ofPubsubItem WHERE serviceID=? AND nodeID=? ORDER BY creationDate DESC LIMIT ?) AS noDelete ON ofPubsubItem.id = noDelete.id WHERE noDelete.id IS NULL AND ofPubsubItem.serviceID = ? AND nodeID = ?]

at org.hsqldb.jdbc.Util.throwError(Unknown Source)

at org.hsqldb.jdbc.jdbcPreparedStatement.(Unknown Source)

at org.hsqldb.jdbc.jdbcConnection.prepareStatement(Unknown Source)

at sun.reflect.GeneratedMethodAccessor4.invoke(Unknown Source)

at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.ja va:43)

at java.lang.reflect.Method.invoke(Method.java:606)

at org.logicalcobwebs.proxool.WrappedConnection.invoke(WrappedConnection.java:162)

at org.logicalcobwebs.proxool.WrappedConnection.intercept(WrappedConnection.java:8 7)

at $java.lang.AutoCloseable$$EnhancerByProxool$$3cc79d38.prepareStatement()

at org.jivesoftware.openfire.pubsub.PubSubPersistenceManager.purgeItems(PubSubPers istenceManager.java:1870)

at org.jivesoftware.openfire.pubsub.PubSubPersistenceManager.access$000(PubSubPers istenceManager.java:62)

at org.jivesoftware.openfire.pubsub.PubSubPersistenceManager$2.run(PubSubPersisten ceManager.java:279)

at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:471)

at java.util.concurrent.FutureTask.run(FutureTask.java:262)

at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145)

at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615)

at java.lang.Thread.run(Thread.java:745)

OF-899 has been filed. Thank you.