diff --git a/pyproject.toml b/pyproject.toml
index 4ff77a3..3374d6a 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -111,7 +111,7 @@ ignore = [
 fixable = ["ALL"]
 
 [tool.black]
-exclude = ["tests"]
+exclude = "tests"
 
 [tool.mypy]
 plugins = [
diff --git a/src/numpydantic/interface/interface.py b/src/numpydantic/interface/interface.py
index 86646a8..50991ea 100644
--- a/src/numpydantic/interface/interface.py
+++ b/src/numpydantic/interface/interface.py
@@ -133,7 +133,7 @@ class Interface(ABC, Generic[T]):
         """Input types for all enabled interfaces"""
         in_types = []
         for iface in cls.interfaces():
-            if isinstance(iface.input_types, tuple | list):
+            if isinstance(iface.input_types, Union[tuple, list]):
                 in_types.extend(iface.input_types)
             else:
                 in_types.append(iface.input_types)
diff --git a/src/numpydantic/types.py b/src/numpydantic/types.py
index 30a5e5b..c629fbf 100644
--- a/src/numpydantic/types.py
+++ b/src/numpydantic/types.py
@@ -6,13 +6,12 @@ Note that these are types as in python typing types, not classes.
 
 # ruff: noqa: D102
 
-from typing import Any, Protocol, Tuple, runtime_checkable
+from typing import Any, Protocol, Tuple, Union, runtime_checkable
 
-import numpy as np
 from nptyping import DType
 
-ShapeType = Tuple[int, ...] | Any
-DtypeType = np.dtype | str | type | Any | DType
+ShapeType = Union[Tuple[int, ...], Any]
+DtypeType = Union[str, type, Any, DType]
 
 
 @runtime_checkable
@@ -25,6 +24,6 @@ class NDArrayType(Protocol):
     @property
     def shape(self) -> ShapeType: ...
 
-    def __getitem__(self, key: int | slice) -> "NDArrayType": ...
+    def __getitem__(self, key: Union[int, slice]) -> "NDArrayType": ...
 
-    def __setitem__(self, key: int | slice, value: "NDArrayType"): ...
+    def __setitem__(self, key: Union[int, slice], value: "NDArrayType"): ...