diff --git a/include/pybind11/pybind11.h b/include/pybind11/pybind11.h
index 82003a909..d3cfb625a 100644
--- a/include/pybind11/pybind11.h
+++ b/include/pybind11/pybind11.h
@@ -1910,7 +1910,7 @@ template <return_value_policy Policy = return_value_policy::reference_internal,
 template <typename InputType, typename OutputType> void implicitly_convertible() {
     struct set_flag {
         bool &flag;
-        set_flag(bool &flag) : flag(flag) { flag = true; }
+        set_flag(bool &flag_) : flag(flag_) { flag_ = true; }
         ~set_flag() { flag = false; }
     };
     auto implicit_caster = [](PyObject *obj, PyTypeObject *type) -> PyObject * {