I found the problem - I was using the wrong version of org.eclipse.jdt.core_X.Y.Z.jar after moving to eclipse-indigo -- View this message in context: http://drools.46999.n3.nabble.com/Error-when-using-Drools-5-4-0-and-jdk-1-7-tp4018975p4019013.html Sent from the Drools: User forum mailing list archive at Nabble.com.