diff --git a/CHANGELOG.md b/CHANGELOG.md
index 2a7850b..3f58736 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,4 +1,7 @@
 # Changelog
+## Pedantic 1.12.10
+- fix tests
+
 ## Pedantic 1.12.9
 - bugfix in type checking logic concerning `typing.Awaitable` and `typing.Coroutine` with return type `UnionType`
 
diff --git a/docs/pedantic/type_checking_logic/check_types.html b/docs/pedantic/type_checking_logic/check_types.html
index 41d7a6b..1ecdb45 100644
--- a/docs/pedantic/type_checking_logic/check_types.html
+++ b/docs/pedantic/type_checking_logic/check_types.html
@@ -584,10 +584,12 @@ <h1 class="title">Module <code>pedantic.type_checking_logic.check_types</code></
     python_sub = _get_class_of_type_annotation(sub_type)
     python_super = _get_class_of_type_annotation(super_type)
 
-    if python_super == typing.Union or isinstance(python_super, types.UnionType):
+    is_union_type_available = hasattr(types, &#39;UnionType&#39;)  # true for Python &gt;= 3.10
+
+    if python_super == typing.Union or (is_union_type_available and isinstance(python_super, types.UnionType)):
         type_args = get_type_arguments(cls=super_type)
 
-        if python_sub == typing.Union or isinstance(python_sub, types.UnionType):
+        if python_sub == typing.Union or (is_union_type_available and isinstance(python_sub, types.UnionType)):
             sub_type_args = get_type_arguments(cls=sub_type)
             return all([x in type_args for x in sub_type_args])
 
diff --git a/pedantic/type_checking_logic/check_types.py b/pedantic/type_checking_logic/check_types.py
index ecc04df..ada455d 100644
--- a/pedantic/type_checking_logic/check_types.py
+++ b/pedantic/type_checking_logic/check_types.py
@@ -555,10 +555,12 @@ def _is_subtype(sub_type: Any, super_type: Any) -> bool:
     python_sub = _get_class_of_type_annotation(sub_type)
     python_super = _get_class_of_type_annotation(super_type)
 
-    if python_super == typing.Union or isinstance(python_super, types.UnionType):
+    is_union_type_available = hasattr(types, 'UnionType')  # true for Python >= 3.10
+
+    if python_super == typing.Union or (is_union_type_available and isinstance(python_super, types.UnionType)):
         type_args = get_type_arguments(cls=super_type)
 
-        if python_sub == typing.Union or isinstance(python_sub, types.UnionType):
+        if python_sub == typing.Union or (is_union_type_available and isinstance(python_sub, types.UnionType)):
             sub_type_args = get_type_arguments(cls=sub_type)
             return all([x in type_args for x in sub_type_args])
 
diff --git a/setup.py b/setup.py
index 317af73..4a2b206 100644
--- a/setup.py
+++ b/setup.py
@@ -14,7 +14,7 @@ def get_content_from_readme(file_name: str = 'README.md') -> str:
 
 setup(
     name="pedantic",
-    version="1.12.9",
+    version="1.12.10",
     python_requires='>=3.7.0',
     packages=find_packages(),
     install_requires=[],