diff --git a/stegano/lsb/lsb.py b/stegano/lsb/lsb.py
index 6dc670d..9dc776f 100644
--- a/stegano/lsb/lsb.py
+++ b/stegano/lsb/lsb.py
@@ -34,7 +34,7 @@ from stegano import tools
 def hide(
     image: Union[str, IO[bytes]],
     message: str,
-    generator: Iterator[int] = None,
+    generator: Union[None, Iterator[int]] = None,
     shift: int = 0,
     encoding: str = "UTF-8",
     auto_convert_rgb: bool = False,
@@ -65,7 +65,7 @@ def hide(
 
 def reveal(
     encoded_image: Union[str, IO[bytes]],
-    generator: Iterator[int] = None,
+    generator: Union[None, Iterator[int]] = None,
     shift: int = 0,
     encoding: str = "UTF-8",
 ):
diff --git a/tests/test_lsb.py b/tests/test_lsb.py
index 998c798..9355b7c 100644
--- a/tests/test_lsb.py
+++ b/tests/test_lsb.py
@@ -229,7 +229,7 @@ class TestLSB(unittest.TestCase):
             lsb.hide(
                 "./tests/sample-files/Lenna.png",
                 message_to_hide,
-                generators.unknown_generator(),
+                generators.unknown_generator(),  # type: ignore
             )
 
     def tearDown(self):