diff --git a/tests/test_utils.py b/tests/test_utils.py
index e84803f15..81fcf9fb4 100644
--- a/tests/test_utils.py
+++ b/tests/test_utils.py
@@ -121,7 +121,7 @@ def test_mark_location():
         ("😀😃", "😀😃".encode()),
     ],
 )
-def test_b(input_str: str, expected: str):
+def test_b(input_str: str, expected: bytes):
     assert pypdf._utils.b_(input_str) == expected