IllegalArgumentException on TimSort

16:15:51,484 ERROR [org.infinispan.interceptors.InvocationContextInterceptor] (http-localhost.localdomain-127.0.0.1-8080-9) ISPN000136: Execution error: java.lang.IllegalArgumentException: Comparison method violates its general contract!
	at org.infinispan.util.TimSort.mergeLo(TimSort.java:751) [infinispan-core-5.1.0.CR4.jar:5.1.0.CR4]
	at org.infinispan.util.TimSort.mergeAt(TimSort.java:487) [infinispan-core-5.1.0.CR4.jar:5.1.0.CR4]
	at org.infinispan.util.TimSort.mergeCollapse(TimSort.java:412) [infinispan-core-5.1.0.CR4.jar:5.1.0.CR4]
	at org.infinispan.util.TimSort.sort(TimSort.java:218) [infinispan-core-5.1.0.CR4.jar:5.1.0.CR4]
	at org.infinispan.util.TimSort.sort(TimSort.java:177) [infinispan-core-5.1.0.CR4.jar:5.1.0.CR4]
	at org.infinispan.interceptors.locking.OptimisticLockingInterceptor.sort(OptimisticLockingInterceptor.java:252) [infinispan-core-5.1.0.CR4.jar:5.1.0.CR4]
	at org.infinispan.interceptors.locking.OptimisticLockingInterceptor.visitPrepareCommand(OptimisticLockingInterceptor.java:94) [infinispan-core-5.1.0.CR4.jar:5.1.0.CR4]
	at org.infinispan.commands.tx.PrepareCommand.acceptVisitor(PrepareCommand.java:131) [infinispan-core-5.1.0.CR4.jar:5.1.0.CR4]
	at org.infinispan.interceptors.base.CommandInterceptor.invokeNextInterceptor(CommandInterceptor.java:116) [infinispan-core-5.1.0.CR4.jar:5.1.0.CR4]
	at org.infinispan.interceptors.NotificationInterceptor.visitPrepareCommand(NotificationInterceptor.java:58) [infinispan-core-5.1.0.CR4.jar:5.1.0.CR4]
	at org.infinispan.commands.tx.PrepareCommand.acceptVisitor(PrepareCommand.java:131) [infinispan-core-5.1.0.CR4.jar:5.1.0.CR4]
	at org.infinispan.interceptors.base.CommandInterceptor.invokeNextInterceptor(CommandInterceptor.java:116) [infinispan-core-5.1.0.CR4.jar:5.1.0.CR4]
	at org.infinispan.interceptors.TxInterceptor.visitPrepareCommand(TxInterceptor.java:106) [infinispan-core-5.1.0.CR4.jar:5.1.0.CR4]
	at org.infinispan.commands.tx.PrepareCommand.acceptVisitor(PrepareCommand.java:131) [infinispan-core-5.1.0.CR4.jar:5.1.0.CR4]
	at org.infinispan.interceptors.base.CommandInterceptor.invokeNextInterceptor(CommandInterceptor.java:116) [infinispan-core-5.1.0.CR4.jar:5.1.0.CR4]
	at org.infinispan.interceptors.StateTransferLockInterceptor.handleWithRetries(StateTransferLockInterceptor.java:201) [infinispan-core-5.1.0.CR4.jar:5.1.0.CR4]
	at org.infinispan.interceptors.StateTransferLockInterceptor.visitPrepareCommand(StateTransferLockInterceptor.java:81) [infinispan-core-5.1.0.CR4.jar:5.1.0.CR4]
	at org.infinispan.commands.tx.PrepareCommand.acceptVisitor(PrepareCommand.java:131) [infinispan-core-5.1.0.CR4.jar:5.1.0.CR4]
	at org.infinispan.interceptors.base.CommandInterceptor.invokeNextInterceptor(CommandInterceptor.java:116) [infinispan-core-5.1.0.CR4.jar:5.1.0.CR4]
	at org.infinispan.interceptors.InvocationContextInterceptor.handleAll(InvocationContextInterceptor.java:116) [infinispan-core-5.1.0.CR4.jar:5.1.0.CR4]
	at org.infinispan.interceptors.InvocationContextInterceptor.handleDefault(InvocationContextInterceptor.java:76) [infinispan-core-5.1.0.CR4.jar:5.1.0.CR4]
	at org.infinispan.commands.AbstractVisitor.visitPrepareCommand(AbstractVisitor.java:113) [infinispan-core-5.1.0.CR4.jar:5.1.0.CR4]
	at org.infinispan.commands.tx.PrepareCommand.acceptVisitor(PrepareCommand.java:131) [infinispan-core-5.1.0.CR4.jar:5.1.0.CR4]
	at org.infinispan.interceptors.base.CommandInterceptor.invokeNextInterceptor(CommandInterceptor.java:116) [infinispan-core-5.1.0.CR4.jar:5.1.0.CR4]
	at org.infinispan.interceptors.BatchingInterceptor.handleDefault(BatchingInterceptor.java:86) [infinispan-core-5.1.0.CR4.jar:5.1.0.CR4]
	at org.infinispan.commands.AbstractVisitor.visitPrepareCommand(AbstractVisitor.java:113) [infinispan-core-5.1.0.CR4.jar:5.1.0.CR4]
	at org.infinispan.commands.tx.PrepareCommand.acceptVisitor(PrepareCommand.java:131) [infinispan-core-5.1.0.CR4.jar:5.1.0.CR4]
	at org.infinispan.interceptors.InterceptorChain.invoke(InterceptorChain.java:345) [infinispan-core-5.1.0.CR4.jar:5.1.0.CR4]
	at org.infinispan.transaction.TransactionCoordinator.commit(TransactionCoordinator.java:159) [infinispan-core-5.1.0.CR4.jar:5.1.0.CR4]
	at org.infinispan.transaction.xa.TransactionXaAdapter.commit(TransactionXaAdapter.java:125) [infinispan-core-5.1.0.CR4.jar:5.1.0.CR4]
	at com.arjuna.ats.internal.jta.resources.arjunacore.XAResourceRecord.topLevelCommit(XAResourceRecord.java:451)