diff --git a/rx/include/rx/die.hpp b/rx/include/rx/die.hpp
index 56e6c6bc1..552aee594 100644
--- a/rx/include/rx/die.hpp
+++ b/rx/include/rx/die.hpp
@@ -1,26 +1,31 @@
 #pragma once
 
 #include "format-base.hpp"
+#include <functional>
+#include <utility>
 
 namespace rx {
+using DieHandler =
+    std::function<void(std::string_view text, std::source_location location)>;
+
+void setDieHandler(DieHandler handler);
+
 namespace detail {
 [[noreturn]] void dieImpl(std::string_view fmt, format_args args,
                           std::source_location location);
 }
 
 template <typename... Args>
-[[noreturn]] void die(rx::format_string_with_location<Args...> fmt,
+[[noreturn]] void die(format_string_with_location<Args...> fmt,
                       const Args &...args) {
-  detail::dieImpl(fmt.get(), make_format_args(const_cast<Args &>(args)...),
-                  fmt.location);
+  detail::dieImpl(fmt.get(), rx::make_format_args(args...), fmt.location);
 }
 
 template <typename... Args>
-void dieIf(bool condition, rx::format_string_with_location<Args...> fmt,
+void dieIf(bool condition, format_string_with_location<Args...> fmt,
            const Args &...args) {
   if (condition) {
-    detail::dieImpl(fmt.get(), make_format_args(const_cast<Args &>(args)...),
-                    fmt.location);
+    detail::dieImpl(fmt.get(), rx::make_format_args(args...), fmt.location);
   }
 }
 } // namespace rx
diff --git a/rx/include/rx/format-base.hpp b/rx/include/rx/format-base.hpp
index 57d5029c8..3f81a4220 100644
--- a/rx/include/rx/format-base.hpp
+++ b/rx/include/rx/format-base.hpp
@@ -41,15 +41,27 @@ struct format_string_impl : fmt::format_string<Args...> {
     return std::string_view(this->str);
   }
 };
+
+template <typename T> struct make_format_arg_type {
+  using type = T &;
+};
+
+template <typename T>
+  requires requires(const T &arg) { fmt::make_format_args(arg); }
+struct make_format_arg_type<T> {
+  using type = const T &;
+};
+
 } // namespace detail
 
 template <typename... Args>
 using format_string = std::type_identity_t<detail::format_string_impl<Args...>>;
 
 template <typename... Args>
-auto make_format_args(const Args &...args)
-    -> decltype(fmt::make_format_args(const_cast<Args &>(args)...)) {
-  return fmt::make_format_args(const_cast<Args &>(args)...);
+auto make_format_args(const Args &...args) -> decltype(fmt::make_format_args(
+    const_cast<detail::make_format_arg_type<Args>::type>(args)...)) {
+  return fmt::make_format_args(
+      const_cast<detail::make_format_arg_type<Args>::type>(args)...);
 }
 
 using fmt::format_to;
diff --git a/rx/include/rx/refl.hpp b/rx/include/rx/refl.hpp
index 9662ce79f..bba608587 100644
--- a/rx/include/rx/refl.hpp
+++ b/rx/include/rx/refl.hpp
@@ -173,6 +173,8 @@ constexpr auto calcFieldCount() {
     return static_cast<std::size_t>(EnumT::_count);
   } else if constexpr (requires { EnumT::count; }) {
     return static_cast<std::size_t>(EnumT::count);
+  } else if constexpr (requires { EnumT::_last; }) {
+    return static_cast<std::size_t>(EnumT::_last) + 1;
   } else if constexpr (!requires { getNameOf<EnumT(N)>()[0]; }) {
     if constexpr (requires { getNameOf<EnumT(N + 1)>()[0]; }) {
       if constexpr (constexpr auto c = getNameOf<EnumT(N + 1)>()[0];
diff --git a/rx/src/die.cpp b/rx/src/die.cpp
index 776ab45a0..62da2b6e0 100644
--- a/rx/src/die.cpp
+++ b/rx/src/die.cpp
@@ -1,18 +1,35 @@
 #include "die.hpp"
 
+#include "print.hpp"
+#include "format-base.hpp"
+
 #include <cstdio>
 #include <cstdlib>
-#include <rx/print.hpp>
+
+
+static rx::DieHandler g_dieHandler;
+
+void rx::setDieHandler(DieHandler handler) {
+  g_dieHandler = std::move(handler);
+}
 
 void rx::detail::dieImpl(std::string_view fmt, format_args args,
                          std::source_location location) {
-  rx::print(stderr, "\n");
-  rx::print(stderr, "{}:{}:{}: ", location.file_name(), location.line(),
-            location.column());
-  rx::vprint_nonunicode(stderr, fmt, args);
-  rx::print(stderr, "\n");
+  if (g_dieHandler != nullptr) {
+    rx::print(stderr, "\n");
+    std::fflush(stdout);
+    std::fflush(stderr);
+
+    g_dieHandler(rx::vformat(fmt, args), location);
+  } else {
+    rx::print(stderr, "\n");
+    rx::print(stderr, "{}:{}:{}: ", location.file_name(), location.line(),
+              location.column());
+    rx::vprint_nonunicode(stderr, fmt, args);
+    rx::print(stderr, "\n");
+    std::fflush(stdout);
+    std::fflush(stderr);
+  }
 
-  std::fflush(stdout);
-  std::fflush(stderr);
   std::abort();
 }