diff --git a/lucene/CHANGES.txt b/lucene/CHANGES.txt
index 1f741fa7cb8..bbd00d8da1e 100644
--- a/lucene/CHANGES.txt
+++ b/lucene/CHANGES.txt
@@ -71,6 +71,11 @@ Changes in Runtime Behavior
   structure of composite and leaf readers.  (Adrien Grand,
   Uwe Schindler)
 
+Build
+
+* LUCENE-6518: Don't report false thread leaks from IBM J9
+  ClassCache Reaper in test framework. (Dawid Weiss)
+
 ======================= Lucene 5.2.0 =======================
 
 New Features
diff --git a/lucene/test-framework/src/java/org/apache/lucene/util/QuickPatchThreadsFilter.java b/lucene/test-framework/src/java/org/apache/lucene/util/QuickPatchThreadsFilter.java
index f2924c2ecb6..8b78ff0caa7 100644
--- a/lucene/test-framework/src/java/org/apache/lucene/util/QuickPatchThreadsFilter.java
+++ b/lucene/test-framework/src/java/org/apache/lucene/util/QuickPatchThreadsFilter.java
@@ -26,15 +26,21 @@ public class QuickPatchThreadsFilter implements ThreadFilter {
   static final boolean isJ9;
   
   static {
-    isJ9 = System.getProperty("java.vm.info", "<?>").contains("IBM J9");
+    isJ9 = Constants.JAVA_VENDOR.startsWith("IBM");
   }
 
   @Override
   public boolean reject(Thread t) {
     if (isJ9) {
+      // LUCENE-6518
+      if ("ClassCache Reaper".equals(t.getName())) {
+        return true;
+      }
+
+      // LUCENE-4736
       StackTraceElement [] stack = t.getStackTrace();
       if (stack.length > 0 && stack[stack.length - 1].getClassName().equals("java.util.Timer$TimerImpl")) {
-        return true; // LUCENE-4736
+        return true;
       }
     }
     return false;