The attached jar file is a self-contained test. Please use the command-line arguments included below to run the test. It will result in a stack trace that shows the UnsupportedOperationException being encountered. Here are the instructions for using the jar file: grab the droolReproducer.jar file and extract it somewhere, i.e. c:\Temp\droolsTest extract it like: "C:\Program Files\IBM\java80_64\sdk\bin\jar" -xvf droolsReproducer.jar cd to C:\temp\droolsTest Place the following jar files in the C:\temp\droolsTest\WEB-INF\lib directory: antlr-runtime-3.5.jar drools-compiler-6.3.0.Final.jar drools-core-6.3.0.Final.jar drools-reteoo-6.3.0.Final.jar kie-api-6.3.0.Final.jar kie-internal-6.3.0.Final.jar log4j-1.2.17.jar mvel2-2.2.6.Final.jar org.eclipse.jdt.core_3.10.0.v20140902-0626.jar protobuf-java-2.5.0.jar slf4j-api-1.7.2.jar slf4j-log4j12-1.7.2.jar xstream-1.4.7.jar run a test case like: "C:\Program Files\IBM\java80_64\sdk\bin\java" -cp C:\temp\droolsTest\WEB-INF\classes;C:\temp\droolsTest\WEB-INF\lib* org.drools.compiler.integrationTests.DroolsTestDriver -test TestUnsupportedOperationException -rbaseDir c:\temp\droolsTest