--- old/src/hotspot/share/gc/z/zPageAllocator.cpp	2019-07-26 14:17:30.324372416 +0200
+++ new/src/hotspot/share/gc/z/zPageAllocator.cpp	2019-07-26 14:17:30.036362964 +0200
@@ -505,6 +505,11 @@
 }
 
 void ZPageAllocator::free_page(ZPage* page, bool reclaimed) {
+  if (reclaimed) {
+    // Clear memory
+    page->clear();
+  }
+
   ZLocker<ZLock> locker(&_lock);
 
   // Update used statistics