diff --git a/include/libimp/result.h b/include/libimp/result.h
index 691fe32..c8f90d7 100644
--- a/include/libimp/result.h
+++ b/include/libimp/result.h
@@ -42,7 +42,7 @@ struct generic_traits {
 
   /// \brief Custom initialization.
   constexpr static void init_code(storage_t &code) noexcept {
-    code = {0, std::make_error_code(std::errc::invalid_argument)};
+    code = {0, std::error_code(-1, std::generic_category())};
   }
   constexpr static void init_code(storage_t &code, T value, std::error_code const &ec) noexcept {
     code = {value, ec};
@@ -73,7 +73,7 @@ struct default_traits<void, ___> {
 
   /// \brief Custom initialization.
   constexpr static void init_code(storage_t &code) noexcept {
-    code = std::make_error_code(std::errc::invalid_argument);
+    code = std::error_code(-1, std::generic_category());
   }
   constexpr static void init_code(storage_t &code, std::error_code const &ec) noexcept {
     code = ec;
@@ -96,7 +96,7 @@ struct default_traits<T, std::enable_if_t<std::is_integral<T>::value>> : generic
   /// \brief Custom initialization.
   constexpr static void init_code(typename generic_traits<T>::storage_t &code, 
                                   T value, bool ok) noexcept {
-    code = {value, ok ? std::error_code() : std::make_error_code(std::errc::invalid_argument)};
+    code = {value, ok ? std::error_code() : std::error_code(-1, std::generic_category())};
   }
   using generic_traits<T>::init_code;
 
@@ -113,7 +113,7 @@ struct default_traits<T, std::enable_if_t<std::is_pointer<T>::value>> : generic_
   }
   constexpr static void init_code(typename generic_traits<T>::storage_t &code, 
                                   std::nullptr_t) noexcept {
-    code = {nullptr, std::make_error_code(std::errc::invalid_argument)};
+    code = {nullptr, std::error_code(-1, std::generic_category())};
   }
   using generic_traits<T>::init_code;
 
diff --git a/test/imp/test_imp_error.cpp b/test/imp/test_imp_error.cpp
index 8693890..8dfb4ef 100644
--- a/test/imp/test_imp_error.cpp
+++ b/test/imp/test_imp_error.cpp
@@ -10,5 +10,5 @@ TEST(error, error_code) {
   std::error_code ecode;
   EXPECT_FALSE(ecode);
   std::cout << ecode.message() << "\n";
-  EXPECT_EQ(ecode.message(), "[generic: 0, \"success\"]");
+  EXPECT_EQ(ecode.message(), "Success");
 }
diff --git a/test/imp/test_imp_result.cpp b/test/imp/test_imp_result.cpp
index dd6248a..efe23b6 100644
--- a/test/imp/test_imp_result.cpp
+++ b/test/imp/test_imp_result.cpp
@@ -102,11 +102,11 @@ TEST(result, fmt) {
     imp::result<int *> r3 {&aaa};
     EXPECT_EQ(imp::fmt(r3), imp::fmt("succ, value = ", (void *)&aaa));
     imp::result<int *> r4 {nullptr};
-    EXPECT_EQ(imp::fmt(r4), imp::fmt("fail, value = ", nullptr, ", error = [generic: 0, \"failure\"]"));
+    EXPECT_EQ(imp::fmt(r4), imp::fmt("fail, value = ", nullptr, ", error = [-1: Unknown error -1]"));
     r4 = {nullptr, std::error_code{1234, std::generic_category()}};
-    EXPECT_EQ(imp::fmt(r4), imp::fmt("fail, value = ", nullptr, ", error = [generic: 1234, \"failure\"]"));
+    EXPECT_EQ(imp::fmt(r4), imp::fmt("fail, value = ", nullptr, ", error = [1234: Unknown error 1234]"));
     imp::result<int *> r5;
-    EXPECT_EQ(imp::fmt(r5), "fail, value = null, error = [generic: 0, \"failure\"]");
+    EXPECT_EQ(imp::fmt(r5), "fail, value = null, error = [-1: Unknown error -1]");
   }
   {
     imp::result<std::int64_t> r1 {-123};
@@ -114,9 +114,9 @@ TEST(result, fmt) {
   }
   {
     imp::result<void> r1;
-    EXPECT_EQ(imp::fmt(r1), "fail, error = [generic: 0, \"failure\"]");
+    EXPECT_EQ(imp::fmt(r1), "fail, error = [-1: Unknown error -1]");
     r1 = std::error_code{};
     EXPECT_TRUE(r1);
-    EXPECT_EQ(imp::fmt(r1), "succ, error = [generic: 0, \"success\"]");
+    EXPECT_EQ(imp::fmt(r1), "succ, error = [0: Success]");
   }
 }
diff --git a/test/imp/test_imp_system.cpp b/test/imp/test_imp_system.cpp
index 51500b8..6ac2629 100644
--- a/test/imp/test_imp_system.cpp
+++ b/test/imp/test_imp_system.cpp
@@ -9,11 +9,6 @@
 #include "libimp/codecvt.h"
 #include "libimp/fmt.h"
 
-#if defined(LIBIMP_OS_WIN)
-#include <Windows.h>
-#else
-#endif
-
 TEST(system, conf) {
   auto ret = imp::sys::conf(imp::sys::info::page_size);
   EXPECT_TRUE(ret);