diff --git a/src/_pytest/mark/structures.py b/src/_pytest/mark/structures.py
index e9e006125..0b1daefd6 100644
--- a/src/_pytest/mark/structures.py
+++ b/src/_pytest/mark/structures.py
@@ -356,7 +356,7 @@ class MarkDecorator:
 
 
 def get_unpacked_marks(
-    obj: object | type,
+    obj: Union[object, type],
     consider_mro: bool = True,
 ) -> List[Mark]:
     """Obtain the unpacked marks that are stored on an object."""