diff --git a/src/cdl_parser/models.py b/src/cdl_parser/models.py
index 2a5078c..05533e2 100644
--- a/src/cdl_parser/models.py
+++ b/src/cdl_parser/models.py
@@ -7,7 +7,7 @@
 from __future__ import annotations
 
 from dataclasses import dataclass, field
-from typing import Any, Union
+from typing import Any
 
 
 @dataclass
@@ -147,7 +147,7 @@ def __str__(self) -> str:
 
 
 # Type alias for form tree nodes
-FormNode = Union[CrystalForm, FormGroup]
+FormNode = CrystalForm | FormGroup
 
 
 @dataclass
diff --git a/tests/test_parser.py b/tests/test_parser.py
index 843163a..39924ca 100644
--- a/tests/test_parser.py
+++ b/tests/test_parser.py
@@ -12,10 +12,8 @@
     POINT_GROUPS,
     CrystalDescription,
     CrystalForm,
-    Definition,
     Feature,
     FormGroup,
-    FormNode,
     MillerIndex,
     ParseError,
     PhenomenonSpec,