Bug: https://bugs.openjdk.java.net/browse/JDK-8233520 Fix: http://cr.openjdk.java.net/~shade/8233520/webrev.01/ This was exposed by recently added assert. But the bug itself is legit Shenandoah bug, and should be fixed everywhere. Testing: affected test; hotspot_gc_shenandoah -- Thanks, -Aleksey