diff --git a/fileformats/generic/tests/test_collection.py b/fileformats/generic/tests/test_collection.py
index 2ba751d..59d3168 100644
--- a/fileformats/generic/tests/test_collection.py
+++ b/fileformats/generic/tests/test_collection.py
@@ -1,3 +1,4 @@
+import sys
 import typing as ty
 import pytest
 from fileformats.generic import Directory, DirectoryOf, SetOf
@@ -70,3 +71,36 @@ def test_set_optional_contents():
     sample_set = SetOf[ty.Optional[MyFormatGz]](my_format)
     assert sample_set.contents == [my_format]
     assert list(sample_set.required_paths()) == [my_format.fspath]
+
+
+@pytest.mark.skipif(sys.version_info < (3, 10), reason="requires python3.10 or higher")
+def test_directory_optional_contents_pep604(tmp_path):
+    my_format = MyFormatGz.sample(dest_dir=tmp_path)
+    sample_dir = DirectoryOf[MyFormatGz](tmp_path)
+    EncodedText.sample(dest_dir=tmp_path)
+    assert sample_dir.contents == [my_format]
+
+    optional_dir = DirectoryOf[MyFormatGz, YourFormat | None](sample_dir)
+    assert optional_dir.contents == [my_format]
+
+    your_format = YourFormat.sample(dest_dir=tmp_path)
+    optional_dir = DirectoryOf[MyFormatGz, YourFormat | None](sample_dir)
+    assert optional_dir.contents == [my_format, your_format]
+
+
+@pytest.mark.skipif(sys.version_info < (3, 10), reason="requires python3.10 or higher")
+def test_set_optional_contents_pep604():
+    my_format = MyFormatGz.sample()
+    your_format = YourFormat.sample()
+
+    sample_set = SetOf[MyFormatGz, YourFormat | None](my_format)
+    assert sample_set.contents == [my_format]
+    assert list(sample_set.required_paths()) == [my_format.fspath]
+
+    sample_set = SetOf[MyFormatGz, YourFormat | None](my_format, your_format)
+    assert sample_set.contents == [my_format, your_format]
+    assert set(sample_set.required_paths()) == {my_format.fspath, your_format.fspath}
+
+    sample_set = SetOf[MyFormatGz | None](my_format)
+    assert sample_set.contents == [my_format]
+    assert list(sample_set.required_paths()) == [my_format.fspath]