diff --git a/tests/test_stl_binders.cpp b/tests/test_stl_binders.cpp
index 583b605d30..ea3ccf5397 100644
--- a/tests/test_stl_binders.cpp
+++ b/tests/test_stl_binders.cpp
@@ -7,6 +7,7 @@
     BSD-style license that can be found in the LICENSE file.
 */
 
+#include <pybind11/attr.h>
 #include <pybind11/numpy.h>
 #include <pybind11/stl_bind.h>
 
@@ -186,6 +187,7 @@ TEST_SUBMODULE(stl_binders, m) {
 
     // test_set_int
     py::bind_set<std::set<int>>(m, "SetInt");
+    // py::implicitly_convertible<py::set, std::set<int>>();
 
     // test_map_string_double
     py::bind_map<std::map<std::string, double>>(m, "MapStringDouble");
diff --git a/tests/test_stl_binders.py b/tests/test_stl_binders.py
index 470bcf2091..50629d4956 100644
--- a/tests/test_stl_binders.py
+++ b/tests/test_stl_binders.py
@@ -153,12 +153,12 @@ def test_set_int():
     s_a = m.SetInt()
     s_b = m.SetInt()
 
-    assert len(s_a) == 0
     assert s_a == s_b
 
     s_a.add(1)
 
     assert 1 in s_a
+    assert len(s_a) == 1
     assert str(s_a) == "SetInt{1}"
     assert s_a != s_b