diff --git a/raillabel_providerkit/validation/validate_onthology/_onthology_classes/_object_classes.py b/raillabel_providerkit/validation/validate_onthology/_onthology_classes/_object_classes.py
index c335237..c4ede47 100644
--- a/raillabel_providerkit/validation/validate_onthology/_onthology_classes/_object_classes.py
+++ b/raillabel_providerkit/validation/validate_onthology/_onthology_classes/_object_classes.py
@@ -12,8 +12,8 @@
 
 @dataclass
 class _ObjectClass:
-    attributes: dict[str, t.Type[_Attribute]]
-    sensor_types: dict[raillabel.format.SensorType, _SensorType]
+    attributes: t.Dict[str, t.Type[_Attribute]]
+    sensor_types: t.Dict[raillabel.format.SensorType, _SensorType]
 
     @classmethod
     def fromdict(cls, data_dict: dict) -> "_ObjectClass":
@@ -103,7 +103,7 @@ def _check_false_attribute_type(
 
     def _compile_applicable_attributes(
         self, annotation: t.Type[raillabel.format._ObjectAnnotation]
-    ) -> dict[str, t.Type[_Attribute]]:
+    ) -> t.Dict[str, t.Type[_Attribute]]:
 
         applicable_attributes = self.attributes
 
diff --git a/raillabel_providerkit/validation/validate_onthology/_onthology_classes/_onthology.py b/raillabel_providerkit/validation/validate_onthology/_onthology_classes/_onthology.py
index c78526c..15e319e 100644
--- a/raillabel_providerkit/validation/validate_onthology/_onthology_classes/_onthology.py
+++ b/raillabel_providerkit/validation/validate_onthology/_onthology_classes/_onthology.py
@@ -11,7 +11,7 @@
 
 @dataclass
 class _Onthology:
-    classes: dict[str, _ObjectClass]
+    classes: t.Dict[str, _ObjectClass]
 
     @classmethod
     def fromdict(cls, data_dict: dict) -> "_Onthology":
diff --git a/raillabel_providerkit/validation/validate_onthology/_onthology_classes/_sensor_type.py b/raillabel_providerkit/validation/validate_onthology/_onthology_classes/_sensor_type.py
index 7bf7258..a74960b 100644
--- a/raillabel_providerkit/validation/validate_onthology/_onthology_classes/_sensor_type.py
+++ b/raillabel_providerkit/validation/validate_onthology/_onthology_classes/_sensor_type.py
@@ -9,7 +9,7 @@
 
 @dataclass
 class _SensorType:
-    attributes: dict[str, t.Type[_Attribute]]
+    attributes: t.Dict[str, t.Type[_Attribute]]
 
     @classmethod
     def fromdict(cls, data_dict: dict) -> "_SensorType":