diff --git a/openfisca_core/indexed_enums/enum.py b/openfisca_core/indexed_enums/enum.py
index 4869e5ba5..b035982ee 100644
--- a/openfisca_core/indexed_enums/enum.py
+++ b/openfisca_core/indexed_enums/enum.py
@@ -67,14 +67,14 @@ def encode(
             return array
 
         # String array
-        if isinstance(array, numpy.ndarray) and array.dtype.kind in {"U", "S"}:
+        if array.dtype.kind in {"U", "S"}:
             array = numpy.select(
                 [array == item.name for item in cls],
                 [item.index for item in cls],
             ).astype(t.ArrayEnum)
 
         # Enum items arrays
-        elif isinstance(array, numpy.ndarray) and array.dtype.kind == "O":
+        elif array.dtype.kind == "O":
             # Ensure we are comparing the comparable. The problem this fixes:
             # On entering this method "cls" will generally come from
             # variable.possible_values, while the array values may come from
@@ -87,12 +87,18 @@ def encode(
             # name to check that the values in the array, if non-empty, are of
             # the right type.
             if len(array) > 0 and cls.__name__ is array[0].__class__.__name__:
-                cls = array[0].__class__
+                klass = array[0].__class__
+
+            else:
+                klass = cls
 
             array = numpy.select(
-                [array == item for item in cls],
-                [item.index for item in cls],
+                [array == item for item in klass],
+                [item.index for item in klass],
             ).astype(t.ArrayEnum)
 
         array = numpy.asarray(array, dtype=t.ArrayEnum)
         return EnumArray(array, cls)
+
+
+__all__ = ["Enum"]
diff --git a/openfisca_core/indexed_enums/enum_array.py b/openfisca_core/indexed_enums/enum_array.py
index de6f83df4..fef8d5386 100644
--- a/openfisca_core/indexed_enums/enum_array.py
+++ b/openfisca_core/indexed_enums/enum_array.py
@@ -151,16 +151,26 @@ def _is_an_enum(self, other: object) -> TypeGuard[t.Enum]:
         if self.possible_values is None:
             raise NotImplementedError
 
+        if other is None:
+            raise NotImplementedError
+
         return (
             not hasattr(other, "__name__")
             and other.__class__.__name__ is self.possible_values.__name__
         )
 
     def _is_an_enum_type(self, other: object) -> TypeGuard[type[t.Enum]]:
+        name: None | str
+
         if self.possible_values is None:
             raise NotImplementedError
 
-        return (
-            hasattr(other, "__name__")
-            and other.__name__ is self.possible_values.__name__
-        )
+        if other is None:
+            raise NotImplementedError
+
+        name = getattr(other, "__name__", None)
+
+        return isinstance(name, str) and name is self.possible_values.__name__
+
+
+__all__ = ["EnumArray"]
diff --git a/openfisca_core/indexed_enums/types.py b/openfisca_core/indexed_enums/types.py
index 57657b8c5..08d0c79e4 100644
--- a/openfisca_core/indexed_enums/types.py
+++ b/openfisca_core/indexed_enums/types.py
@@ -1,12 +1,14 @@
 from __future__ import annotations
 
-from openfisca_core.types import Array as Array
-from openfisca_core.types import ArrayAny as ArrayAny  # noqa: F401
-from openfisca_core.types import ArrayBool as ArrayBool  # noqa: F401
-from openfisca_core.types import ArrayBytes as ArrayBytes  # noqa: F401
-from openfisca_core.types import ArrayEnum as ArrayEnum
-from openfisca_core.types import ArrayInt as ArrayInt  # noqa: F401
-from openfisca_core.types import ArrayStr as ArrayStr  # noqa: F401
+from openfisca_core.types import (
+    Array,
+    ArrayAny,
+    ArrayBool,
+    ArrayBytes,
+    ArrayEnum,
+    ArrayInt,
+    ArrayStr,
+)
 
 import abc
 import enum
@@ -20,3 +22,16 @@ class Enum(enum.Enum):
 
 class EnumArray(Array[ArrayEnum], metaclass=abc.ABCMeta):
     ...
+
+
+__all__ = [
+    "Array",
+    "ArrayAny",
+    "ArrayBool",
+    "ArrayBytes",
+    "ArrayEnum",
+    "ArrayInt",
+    "ArrayStr",
+    "Enum",
+    "EnumArray",
+]