diff --git a/sandbox/grist/objtypes.py b/sandbox/grist/objtypes.py
index 70d36199..37354ffe 100644
--- a/sandbox/grist/objtypes.py
+++ b/sandbox/grist/objtypes.py
@@ -190,7 +190,7 @@ def encode_object(value):
     elif isinstance(value, (list, tuple)):
       return ['L'] + [encode_object(item) for item in value]
     elif isinstance(value, records.RecordSet):
-      return ['r', value._table.table_id, value._row_ids]
+      return ['r', value._table.table_id, value.get_encodable_row_ids()]
     elif isinstance(value, RecordSetStub):
       return ['r', value.table_id, value.row_ids]
     elif isinstance(value, dict):
diff --git a/sandbox/grist/records.py b/sandbox/grist/records.py
index ccbf1c14..9c1e675b 100644
--- a/sandbox/grist/records.py
+++ b/sandbox/grist/records.py
@@ -142,7 +142,7 @@ class RecordSet(object):
     self._table = table
     self._row_ids = row_ids
     self._source_relation = relation or table._identity_relation
-    # If row_ids is itself a RecordSet, default to its _group_by and _sort_by properties.
+    # If row_ids is itself a RecordList, default to its _group_by and _sort_by properties.
     self._group_by = group_by or getattr(row_ids, '_group_by', None)
     self._sort_by = sort_by or getattr(row_ids, '_sort_by', None)
 
@@ -194,6 +194,17 @@ class RecordSet(object):
                                  group_by=self._group_by,
                                  sort_by=self._sort_by)
 
+  def get_encodable_row_ids(self):
+    """
+    Returns stored rowIds as a simple list or tuple type, even if actually stored as RecordList.
+    """
+    # pylint: disable=unidiomatic-typecheck
+    if type(self._row_ids) in (list, tuple):
+      return self._row_ids
+    else:
+      return list(self._row_ids)
+
+
 
 def adjust_record(relation, value):
   """