diff --git a/include/wrenpp/detail/construct_foreign_class.hpp b/include/wrenpp/detail/construct_foreign_class.hpp
index 616d5e6..9d64754 100644
--- a/include/wrenpp/detail/construct_foreign_class.hpp
+++ b/include/wrenpp/detail/construct_foreign_class.hpp
@@ -19,9 +19,13 @@
 
 #include "wrenpp/vm.hpp"
 #include "seters_getters.hpp"
+#if defined(WRENPP_WITH_NAME_GUESSING)
+#	include "guess_class_name.hpp"
+#endif
 #include <utility>
 #include <tuple>
 #include <cassert>
+#include <cstdint>
 
 namespace wren {
 	namespace detail {
@@ -34,12 +38,17 @@ namespace wren {
 			new(memory) T{get<Args>(vm, Indices + 1)...};
 		}
 
+		struct ConstructResult {
+			std::uint16_t parameter_count;
+			bool success;
+		};
+
 		template <typename T, typename... Args>
 		struct ForeignClassHelper;
 
 		template <typename T, template <typename...> class Pack, typename... PackArgs, typename... Args>
 		struct ForeignClassHelper<T, Pack<PackArgs...>, Args...> {
-			static bool construct (VM& vm, int cardinality, void* memory) {
+			static ConstructResult construct (VM& vm, int cardinality, void* memory) {
 				using std::make_integer_sequence;
 
 				//search by number of parameters.
@@ -48,7 +57,7 @@ namespace wren {
 				constexpr int pack_size = static_cast<int>(sizeof...(PackArgs));
 				if (pack_size == cardinality) {
 					construct_single<T, PackArgs...>(make_integer_sequence<int, pack_size>{}, vm, memory);
-					return true;
+					return ConstructResult{pack_size, true};
 				}
 				else {
 					return ForeignClassHelper<T, Args...>::construct(vm, cardinality, memory);
@@ -58,12 +67,12 @@ namespace wren {
 
 		template <typename T, typename LoneArg, typename... Args>
 		struct ForeignClassHelper<T, LoneArg, Args...> {
-			static bool construct (VM& vm, int cardinality, void* memory) {
+			static ConstructResult construct (VM& vm, int cardinality, void* memory) {
 				using std::make_integer_sequence;
 
 				if (1 == cardinality) {
 					construct_single<T, LoneArg>(make_integer_sequence<int, 1>{}, vm, memory);
-					return true;
+					return ConstructResult{1, true};
 				}
 				else {
 					return ForeignClassHelper<T, Args...>::construct(vm, cardinality, memory);
@@ -83,29 +92,19 @@ namespace wren {
 
 		template <typename T>
 		struct ForeignClassHelper<T> {
-			static bool construct (VM& vm, int cardinality, void* memory) {
+			static ConstructResult construct (VM& vm, int cardinality, void* memory) {
 				using std::make_integer_sequence;
 
-				assert(cardinality == 0);
-				construct_single<T>(make_integer_sequence<int, 0>{}, vm, memory);
-				return true;
+				if (cardinality == 0) {
+					construct_single<T>(make_integer_sequence<int, 0>{}, vm, memory);
+					return ConstructResult{0, true};
+				}
+				else {
+					return ConstructResult{static_cast<std::uint16_t>(cardinality), false};
+				}
 			}
 		};
 
-		template <typename T, typename... Args, int... Indices>
-		inline void find_params_and_construct_foreign_class (
-			std::integer_sequence<int, Indices...> seq,
-			VM& vm,
-			void* memory
-		) {
-			if constexpr (sizeof...(Args) == 0) {
-				construct_single<T>(seq, vm, memory);
-			}
-			else {
-				ForeignClassHelper<T, Args...>::construct(vm, vm.slot_count() - 1, memory);
-			}
-		}
-
 		template <std::size_t Search, std::size_t... Values>
 		struct AssertIfDuplicateValues {
 			static_assert(sizeof...(Values) == 0, "Code bug?");
@@ -134,11 +133,17 @@ namespace wren {
 		ret.allocate = [](VM& vm) {
 			void* const mem = vm.set_slot_new_foreign(0, 0, sizeof(T));
 
-			detail::find_params_and_construct_foreign_class<T, Args...>(
-				std::make_integer_sequence<int, sizeof...(Args)>{},
-				vm,
-				mem
-			);
+			const auto result = detail::ForeignClassHelper<T, Args...>::construct(vm, vm.slot_count() - 1, mem);
+			if (not result.success) {
+				set(vm, 1, std::string{"No registered c++ constructor "} +
+#if defined(WRENPP_WITH_NAME_GUESSING)
+					"for class " + guess_class_name<T>() + " " +
+#endif
+					"takes " + std::to_string(result.parameter_count) +
+					" parameter" + (result.parameter_count == 1 ? "" : "s")
+				);
+				vm.abort_fiber(1);
+			}
 		};
 		ret.finalize = [](void* mem) {
 			const auto cale = static_cast<T*>(mem);
diff --git a/include/wrenpp/vm.hpp b/include/wrenpp/vm.hpp
index 72a9968..dcd5f45 100644
--- a/include/wrenpp/vm.hpp
+++ b/include/wrenpp/vm.hpp
@@ -103,6 +103,8 @@ namespace wren {
 		bool has_module (const char* module) const noexcept;
 		bool has_variable (const char* module, const char* name) const noexcept;
 
+		void abort_fiber(int slot_num);
+
 		std::size_t dynafunc_byte_size() const;
 		void reset (Configuration* conf);
 
diff --git a/src/vm.cpp b/src/vm.cpp
index dff58c8..a599d61 100644
--- a/src/vm.cpp
+++ b/src/vm.cpp
@@ -280,6 +280,10 @@ namespace wren {
 		return wrenHasVariable(m_local->wvm, module, name);
 	}
 
+	void VM::abort_fiber(int slot_num) {
+		wrenAbortFiber(m_local->wvm, slot_num);
+	}
+
 	std::size_t VM::dynafunc_byte_size() const {
 		return m_local->dynafunc.total_memory();
 	}