diff --git a/jwst/msaflagopen/tests/test_msa_open.py b/jwst/msaflagopen/tests/test_msa_open.py
index 50e6379984..131c5eba46 100644
--- a/jwst/msaflagopen/tests/test_msa_open.py
+++ b/jwst/msaflagopen/tests/test_msa_open.py
@@ -103,7 +103,7 @@ def test_create_slitlets():
 
     for slit in result:
         # Test the returned data type and fields.
-        assert type(slit) == Slit
+        assert isinstance(slit, Slit)
         assert slit._fields == slit_fields