diff --git a/examples/virtual_.cpp b/examples/virtual_.cpp
index 0ec57ea..b648dd9 100644
--- a/examples/virtual_.cpp
+++ b/examples/virtual_.cpp
@@ -41,7 +41,7 @@ namespace virtual_intrusive {
 class Animal {
   protected:
     boost::openmethod::vptr_type vptr;
-    friend auto boost_openmethod_vptr(const Animal& a) {
+    friend auto boost_openmethod_vptr(const Animal& a, void*) {
         return a.vptr;
     }
 
diff --git a/include/boost/openmethod/core.hpp b/include/boost/openmethod/core.hpp
index a2dea16..ce6affe 100644
--- a/include/boost/openmethod/core.hpp
+++ b/include/boost/openmethod/core.hpp
@@ -301,16 +301,18 @@ constexpr bool is_virtual_ptr = detail::is_virtual_ptr_aux<T>::value;
 
 void boost_openmethod_vptr(...);
 
-template<class Class>
+template<class Registry, class Class>
 constexpr bool has_vptr_fn = std::is_same_v<
-    decltype(boost_openmethod_vptr(std::declval<const Class&>())), vptr_type>;
+    decltype(boost_openmethod_vptr(
+        std::declval<const Class&>(), std::declval<Registry*>())),
+    vptr_type>;
 
 template<class Registry, class ArgType>
 decltype(auto) acquire_vptr(const ArgType& arg) {
     Registry::check_initialized();
 
-    if constexpr (detail::has_vptr_fn<ArgType>) {
-        return boost_openmethod_vptr(arg);
+    if constexpr (detail::has_vptr_fn<Registry, ArgType>) {
+        return boost_openmethod_vptr(arg, static_cast<Registry*>(nullptr));
     } else {
         return Registry::template policy<policies::vptr>::dynamic_vptr(arg);
     }
diff --git a/include/boost/openmethod/default_registry.hpp b/include/boost/openmethod/default_registry.hpp
index 83ccc2b..0c17286 100644
--- a/include/boost/openmethod/default_registry.hpp
+++ b/include/boost/openmethod/default_registry.hpp
@@ -15,23 +15,23 @@
 
 namespace boost::openmethod {
 
-namespace policies {
-
-struct release : registry<
-                     std_rtti, fast_perfect_hash, vptr_vector,
-                     default_error_handler, stderr_output> {};
-
-struct debug
+struct release_registry
     : registry<
-          std_rtti, fast_perfect_hash, vptr_vector, default_error_handler,
-          runtime_checks, stderr_output, trace> {};
+          policies::std_rtti, policies::fast_perfect_hash,
+          policies::vptr_vector, policies::default_error_handler,
+          policies::stderr_output> {};
 
-} // namespace policies
+struct debug_registry
+    : registry<
+          policies::std_rtti, policies::fast_perfect_hash,
+          policies::vptr_vector, policies::default_error_handler,
+          policies::runtime_checks, policies::stderr_output, policies::trace> {
+};
 
 #ifdef NDEBUG
-using default_registry = policies::release;
+using default_registry = release_registry;
 #else
-using default_registry = policies::debug;
+using default_registry = debug_registry;
 #endif // BOOST_OPENMETHOD_DEFAULT_REGISTRY_HPP
 
 } // namespace boost::openmethod
diff --git a/include/boost/openmethod/with_vptr.hpp b/include/boost/openmethod/with_vptr.hpp
index 85163c8..3c379b2 100644
--- a/include/boost/openmethod/with_vptr.hpp
+++ b/include/boost/openmethod/with_vptr.hpp
@@ -76,7 +76,7 @@ class with_vptr_aux<Class, Registry, true> {
         boost_openmethod_vptr = nullptr;
     }
 
-    friend auto boost_openmethod_vptr(const Class& obj) -> vptr_type {
+    friend auto boost_openmethod_vptr(const Class& obj, void*) -> vptr_type {
         if constexpr (Registry::template has_policy<policies::indirect_vptr>) {
             return *obj.boost_openmethod_vptr;
         } else {
@@ -149,8 +149,8 @@ class with_vptr<Class, Base1, Base2, MoreBases...> : detail::with_vptr_derived {
         -> detail::with_vptr_policy<Base1>;
     friend auto boost_openmethod_bases(Class*)
         -> mp11::mp_list<Base1, Base2, MoreBases...>;
-    friend auto boost_openmethod_vptr(const Class& obj) -> vptr_type {
-        return boost_openmethod_vptr(static_cast<const Base1&>(obj));
+    friend auto boost_openmethod_vptr(const Class& obj, void* registry) -> vptr_type {
+        return boost_openmethod_vptr(static_cast<const Base1&>(obj), registry);
     }
 };
 
diff --git a/test/test_core.cpp b/test/test_core.cpp
index 28ec8e3..ce55169 100644
--- a/test/test_core.cpp
+++ b/test/test_core.cpp
@@ -307,3 +307,35 @@ using meet = method<void, void(virtual_<Animal&>, virtual_<Animal&>)>;
 static_assert(has_static_offsets<meet>::value);
 
 } // namespace test_static_slots
+
+namespace TEST_NS {
+
+struct Animal {
+    friend auto boost_openmethod_vptr(const Animal&, void*) -> vptr_type;
+};
+
+static_assert(detail::has_vptr_fn<default_registry, Animal>);
+
+} // namespace TEST_NS
+
+namespace TEST_NS {
+
+using test_registry = test_registry_<__COUNTER__>;
+
+const detail::word value;
+
+struct Animal {
+    friend auto boost_openmethod_vptr(const Animal&, test_registry*) {
+        return &value;
+    }
+};
+
+static_assert(detail::has_vptr_fn<test_registry, Animal>);
+static_assert(!detail::has_vptr_fn<default_registry, Animal>);
+
+BOOST_AUTO_TEST_CASE(vptr_from_function) {
+    initialize<test_registry>();
+    BOOST_TEST(detail::acquire_vptr<test_registry>(Animal{}) == &value);
+}
+
+} // namespace TEST_NS
diff --git a/test/test_virtual_ptr_value_semantics.hpp b/test/test_virtual_ptr_value_semantics.hpp
index 43f7743..1dd2b4f 100644
--- a/test/test_virtual_ptr_value_semantics.hpp
+++ b/test/test_virtual_ptr_value_semantics.hpp
@@ -72,8 +72,8 @@ struct check_illegal_smart_ops {
 
     // policies must be the same
     static_assert(!std::is_constructible_v<
-                  virtual_ptr<smart_ptr<Animal>, policies::debug>,
-                  virtual_ptr<smart_ptr<Animal>, policies::release>>);
+                  virtual_ptr<smart_ptr<Animal>, debug_registry>,
+                  virtual_ptr<smart_ptr<Animal>, release_registry>>);
 
     // a smart virtual_ptr cannot be constructed from a plain reference or
     // pointer