Does not return working copy information when serializing Portal in

Plone 5.2

src/plone/restapi/serializer/dxcontent.py

@@ -6,6 +6,7 @@
 from plone.dexterity.interfaces import IDexterityContainer
 from plone.dexterity.interfaces import IDexterityContent
 from plone.dexterity.utils import iterSchemata
+from plone.restapi import HAS_PLONE_6
 from plone.restapi.batching import HypermediaBatch
 from plone.restapi.deserializer import boolean_value
 from plone.restapi.interfaces import IFieldSerializer
@@ -43,9 +44,16 @@
 
 
 def update_with_working_copy_info(context, result):
-    if WorkingCopyInfo is not None:
-        baseline, working_copy = WorkingCopyInfo(context).get_working_copy_info()
-        result.update({"working_copy": working_copy, "working_copy_of": baseline})
+    if WorkingCopyInfo is None:
+        return
+
+    # Does not return working copy information when serializing Portal in Plone 5.2.
+    if not HAS_PLONE_6 and context.portal_type == "Plone Site":
+        return
+
+    working_copy_info = WorkingCopyInfo(context)
+    baseline, working_copy = working_copy_info.get_working_copy_info()
+    result.update({"working_copy": working_copy, "working_copy_of": baseline})
 
 
 def get_allow_discussion_value(context, request, result):