src/java.base/share/classes/jdk/internal/reflect/UnsafeObjectFieldAccessorImpl.java

@@ -32,11 +32,12 @@
         super(field);
     }
 
     public Object get(Object obj) throws IllegalArgumentException {
         ensureObj(obj);
-        return unsafe.getReference(obj, fieldOffset);
+        return isFlattened() ? unsafe.getValue(obj, fieldOffset, field.getType())
+                             : unsafe.getReference(obj, fieldOffset);
     }
 
     public boolean getBoolean(Object obj) throws IllegalArgumentException {
         throw newGetBooleanIllegalArgumentException();
     }

@@ -74,16 +75,16 @@
     {
         ensureObj(obj);
         if (isFinal) {
             throwFinalFieldIllegalAccessException(value);
         }
-        if (value != null) {
-            if (!field.getType().isAssignableFrom(value.getClass())) {
-                throwSetIllegalArgumentException(value);
-            }
-        }
+        checkValue(value);
+        if (isFlattened()) {
+            unsafe.putValue(obj, fieldOffset, field.getType(), value);
+        } else {
         unsafe.putReference(obj, fieldOffset, value);
+        }
     }
 
     public void setBoolean(Object obj, boolean z)
         throws IllegalArgumentException, IllegalAccessException
     {