diff --git a/include/pybind11/pybind11.h b/include/pybind11/pybind11.h
index 0f2b72cff..efe301e01 100644
--- a/include/pybind11/pybind11.h
+++ b/include/pybind11/pybind11.h
@@ -13,6 +13,7 @@
 #include "detail/class.h"
 #include "detail/dynamic_raw_ptr_cast_if_possible.h"
 #include "detail/init.h"
+#include "detail/native_enum_data.h"
 #include "detail/using_smart_holder.h"
 #include "attr.h"
 #include "gil.h"
@@ -1352,6 +1353,11 @@ public:
         //       For Python 2, reinterpret_borrow was correct.
         return reinterpret_borrow<module_>(m);
     }
+
+    module_ &operator+=(const detail::native_enum_data &data) {
+        detail::native_enum_add_to_parent(*this, data);
+        return *this;
+    }
 };
 
 PYBIND11_NAMESPACE_BEGIN(detail)
@@ -2161,6 +2167,11 @@ public:
         return *this;
     }
 
+    class_ &operator+=(const detail::native_enum_data &data) {
+        detail::native_enum_add_to_parent(*this, data);
+        return *this;
+    }
+
 private:
     /// Initialize holder object, variant 1: object derives from enable_shared_from_this
     template <typename T>
@@ -2619,6 +2630,14 @@ public:
     template <typename... Extra>
     enum_(const handle &scope, const char *name, const Extra &...extra)
         : class_<Type>(scope, name, extra...), m_base(*this, scope) {
+        {
+            if (detail::global_internals_native_enum_type_map_contains(
+                    std::type_index(typeid(Type)))) {
+                pybind11_fail("pybind11::enum_ \"" + std::string(name)
+                              + "\" is already registered as a pybind11::native_enum!");
+            }
+        }
+
         constexpr bool is_arithmetic = detail::any_of<std::is_same<arithmetic, Extra>...>::value;
         constexpr bool is_convertible = std::is_convertible<Type, Underlying>::value;
         m_base.init(is_arithmetic, is_convertible);