diff --git a/tests/conftest.py b/tests/conftest.py
index 58db8e5cbd..7311578461 100644
--- a/tests/conftest.py
+++ b/tests/conftest.py
@@ -9,24 +9,24 @@
 from slither import Slither
 
 
-def pytest_configure(config):
+def pytest_configure(config) -> None:
     """Create a temporary directory for the tests to use."""
     if is_master():
         config.stash["shared_directory"] = tempfile.mkdtemp()
 
 
-def pytest_unconfigure(config):
+def pytest_unconfigure(config) -> None:
     """Remove the temporary directory after the tests are done."""
     if is_master():
         shutil.rmtree(config.stash["shared_directory"])
 
 
-def pytest_configure_node(node):
+def pytest_configure_node(node) -> None:
     """Configure each worker node with the shared directory."""
     node.workerinput["shared_directory"] = node.config.stash["shared_directory"]
 
 
-def is_master():
+def is_master() -> bool:
     """Returns True if the current process is the master process (which does not have a worker id)."""
     return os.environ.get("PYTEST_XDIST_WORKER") is None
 
diff --git a/tests/unit/core/test_literal.py b/tests/unit/core/test_literal.py
index 569b6eec73..2622090c54 100644
--- a/tests/unit/core/test_literal.py
+++ b/tests/unit/core/test_literal.py
@@ -89,3 +89,10 @@ def test_not_equal_to_non_literal(self):
         lit = Literal("100", "uint256")
         assert lit != "100"
         assert lit != 100
+        assert lit != None
+
+    def test_equal_none_subdenomination(self):
+        """Literals with None and absent subdenomination should be equal."""
+        lit1 = Literal("100", "uint256")
+        lit2 = Literal("100", "uint256", subdenomination=None)
+        assert lit1 == lit2