diff --git a/tiledb/tests/test_schema_evolution.py b/tiledb/tests/test_schema_evolution.py
index efadd0a741..27376f0824 100644
--- a/tiledb/tests/test_schema_evolution.py
+++ b/tiledb/tests/test_schema_evolution.py
@@ -260,21 +260,21 @@ def test_schema_evolution_drop_fixed_attribute_and_add_back_as_var_sized(tmp_pat
         assert A.schema.attr("b").dtype == np.int32
 
     se = tiledb.ArraySchemaEvolution(ctx)
-    newattr = tiledb.Attr("a", dtype="S", var=True)
+    newattr = tiledb.Attr("a", dtype="U", var=True)
     se.add_attribute(newattr)
     se.array_evolve(uri)
 
     # check schema and data after adding attribute back as a var-sized attribute
     with tiledb.open(uri) as A:
         assert A.schema.has_attr("a")
-        assert A.schema.attr("a").dtype == "S"
+        assert A.schema.attr("a").dtype == "U"
         assert A.schema.attr("b").dtype == np.int32
         # check that each value == b'\x80' (empty byte)
-        assert_array_equal(A[:]["a"], np.array([b"\x80" for _ in range(10)]))
+        assert_array_equal(A[:]["a"], np.array(["" for _ in range(10)]))
 
     # add new data to the array
     new_data = np.array(
-        ["tiledb-string-n.{}".format(i) for i in range(1, 11)], dtype="S"
+        ["tiledb-string-n.{}".format(i) for i in range(1, 11)], dtype="U"
     )
     with tiledb.open(uri, "w") as A:
         A[:] = {"a": new_data, "b": original_data}