diff --git a/tests/test_compat.py b/tests/test_compat.py
index 33b0e17723..36066a2557 100644
--- a/tests/test_compat.py
+++ b/tests/test_compat.py
@@ -121,8 +121,10 @@ def test_serialize_sequence_value_with_optional_list_pipe_union():
 def test_serialize_sequence_value_with_none_first_in_union():
     """Test that serialize_sequence_value handles Union[None, List[...]] correctly."""
     from fastapi._compat import v2
+    from typing import Union
 
-    field_info = FieldInfo(annotation=list[str] | None)
+    # Use Union[None, list[str]] to ensure None comes first in the union args
+    field_info = FieldInfo(annotation=Union[None, list[str]])
     field = v2.ModelField(name="items", field_info=field_info)
     result = v2.serialize_sequence_value(field=field, value=["x", "y"])
     assert result == ["x", "y"]