--- old/src/jdk.hotspot.agent/share/classes/sun/jvm/hotspot/gc/z/ZPageTableEntry.java	2019-02-13 16:35:06.482271213 +0100
+++ new/src/jdk.hotspot.agent/share/classes/sun/jvm/hotspot/gc/z/ZPageTableEntry.java	2019-02-13 16:35:06.082271227 +0100
@@ -35,10 +35,18 @@
     }
 
     ZPage page() {
-        return (ZPage)VMObjectFactory.newObject(ZPage.class, entry.andWithMask(~1L));
+        return (ZPage)VMObjectFactory.newObject(ZPage.class, zPageBits());
+    }
+
+    private Address zPageBits() {
+        return entry.andWithMask(~1L);
     }
 
     boolean relocating() {
         return (entry.asLongValue() & 1) == 1;
     }
+
+    boolean isEmpty() {
+        return entry == null || zPageBits() == null;
+    }
 }