diff --git a/osc/util/models.py b/osc/util/models.py
index 061374cb..8d6b3c4a 100644
--- a/osc/util/models.py
+++ b/osc/util/models.py
@@ -39,6 +39,15 @@ if sys.version_info < (3, 8):
 else:
     from typing import get_origin
 
+
+# types.UnionType was added in Python 3.10
+if sys.version_info < (3, 10):
+    class UnionType:
+        pass
+else:
+    from types import UnionType
+
+
 import urllib3.response
 
 from . import xml
@@ -79,8 +88,9 @@ class FromParent(NotSetClass):
     def __repr__(self):
         return f"FromParent(field_name={self.field_name})"
 
-
-class Field(property):
+# HACK: inheriting from Any fixes the following mypy error:
+#       Incompatible types in assignment (expression has type "Field", variable has type "X | None")  [assignment]
+class Field(property, *([Any] if typing.TYPE_CHECKING else [])):
     def __init__(
         self,
         default: Any = NotSet,
@@ -165,7 +175,7 @@ class Field(property):
     @property
     def is_optional(self):
         origin_type = get_origin(self.type) or self.type
-        return origin_type == Union and len(self.type.__args__) == 2 and type(None) in self.type.__args__
+        return origin_type in (Union, UnionType) and type(None) in self.type.__args__
 
     @property
     def is_model(self):
@@ -193,7 +203,7 @@ class Field(property):
             origin_type = get_origin(expected_type) or expected_type
 
             # unwrap Union
-            if origin_type == Union:
+            if origin_type in (Union, UnionType):
                 if value is None and type(None) in expected_type.__args__:
                     valid_type = True
                     continue
@@ -464,7 +474,7 @@ class BaseModel(metaclass=ModelMeta):
 
 
 class XmlModel(BaseModel):
-    XML_TAG = None
+    XML_TAG: Optional[str] = None
 
     _apiurl: Optional[str] = Field(
         exclude=True,
diff --git a/tests/test_models.py b/tests/test_models.py
index 29d0a6a3..04756ead 100644
--- a/tests/test_models.py
+++ b/tests/test_models.py
@@ -1,3 +1,4 @@
+import sys
 import unittest
 from typing import Set
 
@@ -24,6 +25,16 @@ class TestNotSet(unittest.TestCase):
 
 
 class Test(unittest.TestCase):
+    @unittest.skipIf(sys.version_info[:2] < (3, 10), "added in python 3.10")
+    def test_union_or(self):
+        class TestModel(BaseModel):
+            text: str | None = Field()
+
+        m = TestModel()
+        self.assertEqual(m.dict(), {"text": None})
+
+        self.assertRaises(TypeError, setattr, m.text, 123)
+
     def test_dict(self):
         class TestSubmodel(BaseModel):
             text: str = Field(default="default")