SingleFileStoreStressTest.testWritesAndClear && SingleFileStoreFunctionalTest.testParsingEmptyElement fail with IBM6 JDK

Following exception is thrown
java.util.concurrent.ExecutionException: java.lang.Exception: org.infinispan.persistence.spi.PersistenceException: java.lang.NullPointerException
at java.util.concurrent.FutureTask$Sync.innerGet(FutureTask.java:233)
at java.util.concurrent.FutureTask.get(FutureTask.java:94)
at org.infinispan.persistence.file.SingleFileStoreStressTest.testWritesAndClear(SingleFileStoreStressTest.java:127)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:60)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:37)
at java.lang.reflect.Method.invoke(Method.java:611)
at org.testng.internal.MethodInvocationHelper.invokeMethod(MethodInvocationHelper.java:80)
at org.testng.internal.Invoker.invokeMethod(Invoker.java:715)
at org.testng.internal.Invoker.invokeTestMethod(Invoker.java:907)
at org.testng.internal.Invoker.invokeTestMethods(Invoker.java:1237)
at org.testng.internal.TestMethodWorker.invokeTestMethods(TestMethodWorker.java:127)
at org.testng.internal.TestMethodWorker.run(TestMethodWorker.java:111)
at org.testng.TestRunner.privateRun(TestRunner.java:767)
at org.testng.TestRunner.run(TestRunner.java:617)
at org.testng.SuiteRunner.runTest(SuiteRunner.java:334)
at org.testng.SuiteRunner.access$000(SuiteRunner.java:37)
at org.testng.SuiteRunner$SuiteWorker.run(SuiteRunner.java:368)
at org.testng.internal.thread.ThreadUtil$2.call(ThreadUtil.java:64)
at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:314)
at java.util.concurrent.FutureTask.run(FutureTask.java:149)
at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:908)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:931)
at java.lang.Thread.run(Thread.java:738)
Caused by: java.lang.Exception: org.infinispan.persistence.spi.PersistenceException: java.lang.NullPointerException
at org.infinispan.persistence.file.SingleFileStoreStressTest$StopOnExceptionTask.call(SingleFileStoreStressTest.java:257)
at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:314)
at java.util.concurrent.FutureTask.run(FutureTask.java:149)
... 1 more
Caused by: org.infinispan.persistence.spi.PersistenceException: java.lang.NullPointerException
at org.infinispan.persistence.file.SingleFileStore.write(SingleFileStore.java:317)
at org.infinispan.persistence.file.SingleFileStoreStressTest$WriteTask.call(SingleFileStoreStressTest.java:169)
at org.infinispan.persistence.file.SingleFileStoreStressTest$StopOnExceptionTask.call(SingleFileStoreStressTest.java:254)
... 3 more
Caused by: java.lang.NullPointerException
at java.util.TreeMap$AbstractSubMapIterator.remove(TreeMap.java:218)
at org.infinispan.persistence.file.SingleFileStore.allocate(SingleFileStore.java:242)
at org.infinispan.persistence.file.SingleFileStore.write(SingleFileStore.java:284)
... 5 more

You can check all 5 builds were running here
https://jenkins.mw.lab.eng.bos.redhat.com/hudson/view/JDG/view/FUNC/job/edg-60-ispn-testsuite-rhel-ibm6/USE_JDK=JDK6,jdk=ibm17,label=RHEL6_x86/