diff --git a/src/hotspot/share/gc/z/zDebug.gdb b/src/hotspot/share/gc/z/zDebug.gdb
index f27266c05b5..df087c4a42d 100644
--- a/src/hotspot/share/gc/z/zDebug.gdb
+++ b/src/hotspot/share/gc/z/zDebug.gdb
@@ -50,7 +50,7 @@ define zpo
     end
     printf "\t Page: %llu\n", ((uintptr_t)$obj & ZAddressOffsetMask) >> ZGranuleSizeShift
     x/16gx $obj
-    set $klass = (Klass*)(void*)((uintptr_t)CompressedKlassPointers::_base +((uintptr_t)$obj->_metadata->_compressed_klass << CompressedKlassPointers::_shift))
+    set $klass = (Klass*)(void*)((uintptr_t)CompressedKlassPointers::_base +((uintptr_t)$obj->_compressed_klass << CompressedKlassPointers::_shift))
     printf "Mark:  0x%016llx\tKlass: %s\n", (uintptr_t)$obj->_mark, (char*)$klass->_name->_body
 end
 
diff --git a/src/hotspot/share/jvmci/vmStructs_jvmci.cpp b/src/hotspot/share/jvmci/vmStructs_jvmci.cpp
index 91482e825cd..4b74a290331 100644
--- a/src/hotspot/share/jvmci/vmStructs_jvmci.cpp
+++ b/src/hotspot/share/jvmci/vmStructs_jvmci.cpp
@@ -342,7 +342,7 @@
   volatile_nonstatic_field(ObjectMonitor,      _succ,                                         int64_t)                               \
                                                                                                                                      \
   volatile_nonstatic_field(oopDesc,            _mark,                                         markWord)                              \
-  volatile_nonstatic_field(oopDesc,            _metadata._klass,                              Klass*)                                \
+  volatile_nonstatic_field(oopDesc,            _compressed_klass,                             narrowKlass)                           \
                                                                                                                                      \
   static_field(StubRoutines,                _verify_oop_count,                                jint)                                  \
                                                                                                                                      \
diff --git a/src/hotspot/share/oops/oop.cpp b/src/hotspot/share/oops/oop.cpp
index ac8d453fe9d..5990a448b9d 100644
--- a/src/hotspot/share/oops/oop.cpp
+++ b/src/hotspot/share/oops/oop.cpp
@@ -152,7 +152,7 @@ bool oopDesc::is_typeArray_noinline()   const { return is_typeArray();   }
 #if INCLUDE_CDS_JAVA_HEAP
 void oopDesc::set_narrow_klass(narrowKlass nk) {
   assert(CDSConfig::is_dumping_heap(), "Used by CDS only. Do not abuse!");
-  _metadata._compressed_klass = nk;
+  _compressed_klass = nk;
 }
 #endif
 
diff --git a/src/hotspot/share/oops/oop.hpp b/src/hotspot/share/oops/oop.hpp
index 0dc6590750e..80fe290431c 100644
--- a/src/hotspot/share/oops/oop.hpp
+++ b/src/hotspot/share/oops/oop.hpp
@@ -49,10 +49,7 @@ class oopDesc {
   friend class JVMCIVMStructs;
  private:
   volatile markWord _mark;
-  union _metadata {
-    Klass*      _klass;
-    narrowKlass _compressed_klass;
-  } _metadata;
+  narrowKlass _compressed_klass;
 
   // There may be ordering constraints on the initialization of fields that
   // make use of the C++ copy/assign incorrect.
@@ -338,7 +335,7 @@ class oopDesc {
     } else
 #endif
     {
-      return (int)offset_of(oopDesc, _metadata._klass);
+      return (int)offset_of(oopDesc, _compressed_klass);
     }
   }
   static int klass_gap_offset_in_bytes() {
diff --git a/src/hotspot/share/oops/oop.inline.hpp b/src/hotspot/share/oops/oop.inline.hpp
index ced8025d4bf..62da6404162 100644
--- a/src/hotspot/share/oops/oop.inline.hpp
+++ b/src/hotspot/share/oops/oop.inline.hpp
@@ -99,7 +99,7 @@ Klass* oopDesc::klass() const {
     case ObjLayout::Compact:
       return mark().klass();
     case ObjLayout::Compressed:
-      return CompressedKlassPointers::decode_not_null(_metadata._compressed_klass);
+      return CompressedKlassPointers::decode_not_null(_compressed_klass);
     default:
       ShouldNotReachHere();
   }
@@ -110,7 +110,7 @@ Klass* oopDesc::klass_or_null() const {
     case ObjLayout::Compact:
       return mark().klass_or_null();
     case ObjLayout::Compressed:
-      return CompressedKlassPointers::decode(_metadata._compressed_klass);
+      return CompressedKlassPointers::decode(_compressed_klass);
     default:
       ShouldNotReachHere();
   }
@@ -121,7 +121,7 @@ Klass* oopDesc::klass_or_null_acquire() const {
     case ObjLayout::Compact:
       return mark_acquire().klass();
     case ObjLayout::Compressed: {
-      narrowKlass narrow_klass = AtomicAccess::load_acquire(&_metadata._compressed_klass);
+      narrowKlass narrow_klass = AtomicAccess::load_acquire(&_compressed_klass);
       return CompressedKlassPointers::decode(narrow_klass);
     }
     default:
@@ -134,7 +134,7 @@ Klass* oopDesc::klass_without_asserts() const {
     case ObjLayout::Compact:
       return mark().klass_without_asserts();
     case ObjLayout::Compressed:
-      return CompressedKlassPointers::decode_without_asserts(_metadata._compressed_klass);
+      return CompressedKlassPointers::decode_without_asserts(_compressed_klass);
     default:
       ShouldNotReachHere();
   }
@@ -145,7 +145,7 @@ narrowKlass oopDesc::narrow_klass() const {
     case ObjLayout::Compact:
       return mark().narrow_klass();
     case ObjLayout::Compressed:
-      return _metadata._compressed_klass;
+      return _compressed_klass;
     default:
       ShouldNotReachHere();
   }
@@ -154,7 +154,7 @@ narrowKlass oopDesc::narrow_klass() const {
 void oopDesc::set_klass(Klass* k) {
   assert(Universe::is_bootstrapping() || (k != nullptr && k->is_klass()), "incorrect Klass");
   assert(!UseCompactObjectHeaders, "don't set Klass* with compact headers");
-  _metadata._compressed_klass = CompressedKlassPointers::encode_not_null(k);
+  _compressed_klass = CompressedKlassPointers::encode_not_null(k);
 }
 
 void oopDesc::release_set_klass(HeapWord* mem, Klass* k) {
diff --git a/src/hotspot/share/runtime/vmStructs.cpp b/src/hotspot/share/runtime/vmStructs.cpp
index f65a3441bf4..d1cfe55b8bf 100644
--- a/src/hotspot/share/runtime/vmStructs.cpp
+++ b/src/hotspot/share/runtime/vmStructs.cpp
@@ -162,8 +162,7 @@
   /******************************************************************/                                                               \
                                                                                                                                      \
   volatile_nonstatic_field(oopDesc,            _mark,                                         markWord)                              \
-  volatile_nonstatic_field(oopDesc,            _metadata._klass,                              Klass*)                                \
-  volatile_nonstatic_field(oopDesc,            _metadata._compressed_klass,                   narrowKlass)                           \
+  volatile_nonstatic_field(oopDesc,            _compressed_klass,                             narrowKlass)                           \
   static_field(BarrierSet,                     _barrier_set,                                  BarrierSet*)                           \
   nonstatic_field(ArrayKlass,                  _dimension,                                    int)                                   \
   volatile_nonstatic_field(ArrayKlass,         _higher_dimension,                             ObjArrayKlass*)                        \
diff --git a/src/jdk.hotspot.agent/share/classes/sun/jvm/hotspot/oops/Oop.java b/src/jdk.hotspot.agent/share/classes/sun/jvm/hotspot/oops/Oop.java
index 2a49845eaad..e54d93068d7 100644
--- a/src/jdk.hotspot.agent/share/classes/sun/jvm/hotspot/oops/Oop.java
+++ b/src/jdk.hotspot.agent/share/classes/sun/jvm/hotspot/oops/Oop.java
@@ -51,8 +51,7 @@ public class Oop {
       headerSize = markType.getSize();
     } else {
       headerSize = type.getSize();
-      klass      = new MetadataField(type.getAddressField("_metadata._klass"), 0);
-      compressedKlass  = new NarrowKlassField(type.getAddressField("_metadata._compressed_klass"), 0);
+      compressedKlass  = new NarrowKlassField(type.getAddressField("_compressed_klass"), 0);
     }
   }
 
@@ -75,7 +74,6 @@ public class Oop {
   public  static long getHeaderSize() { return headerSize; } // Header size in bytes.
 
   private static CIntField mark;
-  private static MetadataField  klass;
   private static NarrowKlassField compressedKlass;
 
   // Accessors for declared fields