diff --git a/src/datamaestro/record.py b/src/datamaestro/record.py
index 7f85f6a..23d7324 100644
--- a/src/datamaestro/record.py
+++ b/src/datamaestro/record.py
@@ -1,5 +1,5 @@
 import logging
-from typing import ClassVar, Type, TypeVar, Dict, List, Union, Optional, Set
+from typing import ClassVar, Type, TypeVar, Dict, List, Union, Optional, FrozenSet
 
 
 class Item:
@@ -131,7 +131,7 @@ def update(self, *items: T) -> "Record":
 
     # --- Class methods and variables
 
-    itemtypes: ClassVar[Optional[Set[Type[T]]]] = []
+    itemtypes: ClassVar[Optional[FrozenSet[Type[T]]]] = []
     """For specific records, this is the list of types. The value is null when
     no validation is used (e.g. pickled records created on the fly)"""
 
@@ -182,7 +182,7 @@ def from_types(cls, name: str, *itemtypes: Type[T], module: str = None):
     __RECORD_TYPES_CACHE__: Dict[frozenset, Type["Record"]] = {}
 
     @staticmethod
-    def fromitemtypes(itemtypes: Set[T]):
+    def fromitemtypes(itemtypes: FrozenSet[T]):
         if recordtype := Record.__RECORD_TYPES_CACHE__.get(itemtypes, None):
             return recordtype
 
@@ -227,7 +227,7 @@ def get(self, record_type: Type[Record]):
 
         updated_type = record_type.from_types(
             f"{self._name}_{record_type.__name__}",
-            *self._itemtypes,
+            *(itemtype.__get_base__() for itemtype in self._itemtypes),
             module=self._module,
         )
         self._cache[record_type] = updated_type
diff --git a/src/datamaestro/test/test_record.py b/src/datamaestro/test/test_record.py
index e564fa5..8e5725d 100644
--- a/src/datamaestro/test/test_record.py
+++ b/src/datamaestro/test/test_record.py
@@ -19,6 +19,11 @@ class BItem(Item):
     b: int
 
 
+@define
+class B1Item(BItem):
+    b1: int
+
+
 @define
 class CItem(Item):
     c: int
@@ -110,3 +115,7 @@ def test_record_pickled():
 
     # This is OK
     cache.update(r, CItem(4), cls=MyRecord)
+
+    # --- Test when we update a pickled record with an of a sub-class
+    cache = RecordTypesCache("OnTheFly", B1Item)
+    r2 = cache.update(r, B1Item(1, 2))