diff --git a/include/pybind11/detail/smart_holder_poc.h b/include/pybind11/detail/smart_holder_poc.h
index e169f2f26..d0140d6dc 100644
--- a/include/pybind11/detail/smart_holder_poc.h
+++ b/include/pybind11/detail/smart_holder_poc.h
@@ -48,6 +48,7 @@ Details:
 
 #pragma once
 
+#include <functional>
 #include <memory>
 #include <stdexcept>
 #include <string>
@@ -67,15 +68,17 @@ static constexpr bool type_has_shared_from_this(const std::enable_shared_from_th
     return true;
 }
 
+struct smart_holder;
+
 struct guarded_delete {
     std::weak_ptr<void> released_ptr; // Trick to keep the smart_holder memory footprint small.
-    void (*del_ptr)(void *);
+    std::function<void(void *)> del_fun;
     bool armed_flag;
-    guarded_delete(void (*del_ptr)(void *), bool armed_flag)
-        : del_ptr{del_ptr}, armed_flag{armed_flag} {}
+    guarded_delete(std::function<void(void *)> &&del_fun, bool armed_flag)
+        : del_fun{std::move(del_fun)}, armed_flag{armed_flag} {}
     void operator()(void *raw_ptr) const {
         if (armed_flag) {
-            (*del_ptr)(raw_ptr);
+            del_fun(raw_ptr);
         }
     }
 };
@@ -99,13 +102,10 @@ guarded_delete make_guarded_builtin_delete(bool armed_flag) {
 }
 
 template <typename T, typename D>
-inline void custom_delete(void *raw_ptr) {
-    D()(static_cast<T *>(raw_ptr));
-}
-
-template <typename T, typename D>
-guarded_delete make_guarded_custom_deleter(bool armed_flag) {
-    return guarded_delete(custom_delete<T, D>, armed_flag);
+guarded_delete make_guarded_custom_deleter(D &&uqp_del, bool armed_flag) {
+    return guarded_delete(std::function<void(void *)>(
+                              [&uqp_del](void *raw_ptr) { uqp_del(static_cast<T *>(raw_ptr)); }),
+                          armed_flag);
 }
 
 template <typename T>
@@ -309,7 +309,7 @@ struct smart_holder {
         if (hld.vptr_is_using_builtin_delete) {
             gd = make_guarded_builtin_delete<T>(true);
         } else {
-            gd = make_guarded_custom_deleter<T, D>(true);
+            gd = make_guarded_custom_deleter<T, D>(std::move(unq_ptr.get_deleter()), true);
         }
         if (void_ptr != nullptr) {
             hld.vptr.reset(void_ptr, std::move(gd));