diff --git a/classpath/java/lang/Thread.java b/classpath/java/lang/Thread.java
index 095691d342..5d99c2f092 100644
--- a/classpath/java/lang/Thread.java
+++ b/classpath/java/lang/Thread.java
@@ -14,6 +14,9 @@ import java.util.Map;
 import java.util.WeakHashMap;
 
 public class Thread implements Runnable {
+  // set and accessed from within LockSupport
+  protected volatile Object parkBlocker;
+  
   private long peer;
   private volatile boolean interrupted;
   private volatile boolean unparked;