diff --git a/libcxx/test/std/diagnostics/syserr/syserr.syserr/syserr.syserr.members/ctor_error_code.pass.cpp b/libcxx/test/std/diagnostics/syserr/syserr.syserr/syserr.syserr.members/ctor_error_code.pass.cpp
--- a/libcxx/test/std/diagnostics/syserr/syserr.syserr/syserr.syserr.members/ctor_error_code.pass.cpp
+++ b/libcxx/test/std/diagnostics/syserr/syserr.syserr/syserr.syserr.members/ctor_error_code.pass.cpp
@@ -17,11 +17,13 @@
 #include <system_error>
 #include <string>
 #include <cassert>
+#include <clocale>
 
 #include "test_macros.h"
 
 int main(int, char**)
 {
+    std::setlocale (LC_ALL, "C");
     std::system_error se(static_cast<int>(std::errc::not_a_directory),
                          std::generic_category(), "some text");
     assert(se.code() == std::make_error_code(std::errc::not_a_directory));
diff --git a/libcxx/test/std/diagnostics/syserr/syserr.syserr/syserr.syserr.members/ctor_error_code_const_char_pointer.pass.cpp b/libcxx/test/std/diagnostics/syserr/syserr.syserr/syserr.syserr.members/ctor_error_code_const_char_pointer.pass.cpp
--- a/libcxx/test/std/diagnostics/syserr/syserr.syserr/syserr.syserr.members/ctor_error_code_const_char_pointer.pass.cpp
+++ b/libcxx/test/std/diagnostics/syserr/syserr.syserr/syserr.syserr.members/ctor_error_code_const_char_pointer.pass.cpp
@@ -17,11 +17,13 @@
 #include <system_error>
 #include <string>
 #include <cassert>
+#include <clocale>
 
 #include "test_macros.h"
 
 int main(int, char**)
 {
+    std::setlocale (LC_ALL, "C");
     std::string what_arg("test message");
     std::system_error se(make_error_code(std::errc::not_a_directory), what_arg.c_str());
     assert(se.code() == std::make_error_code(std::errc::not_a_directory));
diff --git a/libcxx/test/std/diagnostics/syserr/syserr.syserr/syserr.syserr.members/ctor_error_code_string.pass.cpp b/libcxx/test/std/diagnostics/syserr/syserr.syserr/syserr.syserr.members/ctor_error_code_string.pass.cpp
--- a/libcxx/test/std/diagnostics/syserr/syserr.syserr/syserr.syserr.members/ctor_error_code_string.pass.cpp
+++ b/libcxx/test/std/diagnostics/syserr/syserr.syserr/syserr.syserr.members/ctor_error_code_string.pass.cpp
@@ -17,11 +17,13 @@
 #include <system_error>
 #include <string>
 #include <cassert>
+#include <clocale>
 
 #include "test_macros.h"
 
 int main(int, char**)
 {
+    std::setlocale (LC_ALL, "C");
     std::string what_arg("test message");
     std::system_error se(make_error_code(std::errc::not_a_directory), what_arg);
     assert(se.code() == std::make_error_code(std::errc::not_a_directory));
diff --git a/libcxx/test/std/diagnostics/syserr/syserr.syserr/syserr.syserr.members/ctor_int_error_category.pass.cpp b/libcxx/test/std/diagnostics/syserr/syserr.syserr/syserr.syserr.members/ctor_int_error_category.pass.cpp
--- a/libcxx/test/std/diagnostics/syserr/syserr.syserr/syserr.syserr.members/ctor_int_error_category.pass.cpp
+++ b/libcxx/test/std/diagnostics/syserr/syserr.syserr/syserr.syserr.members/ctor_int_error_category.pass.cpp
@@ -17,11 +17,13 @@
 #include <system_error>
 #include <string>
 #include <cassert>
+#include <clocale>
 
 #include "test_macros.h"
 
 int main(int, char**)
 {
+    std::setlocale (LC_ALL, "C");
     std::system_error se(static_cast<int>(std::errc::not_a_directory),
                          std::generic_category());
     assert(se.code() == std::make_error_code(std::errc::not_a_directory));
diff --git a/libcxx/test/std/diagnostics/syserr/syserr.syserr/syserr.syserr.members/ctor_int_error_category_const_char_pointer.pass.cpp b/libcxx/test/std/diagnostics/syserr/syserr.syserr/syserr.syserr.members/ctor_int_error_category_const_char_pointer.pass.cpp
--- a/libcxx/test/std/diagnostics/syserr/syserr.syserr/syserr.syserr.members/ctor_int_error_category_const_char_pointer.pass.cpp
+++ b/libcxx/test/std/diagnostics/syserr/syserr.syserr/syserr.syserr.members/ctor_int_error_category_const_char_pointer.pass.cpp
@@ -17,11 +17,13 @@
 #include <system_error>
 #include <string>
 #include <cassert>
+#include <clocale>
 
 #include "test_macros.h"
 
 int main(int, char**)
 {
+    std::setlocale (LC_ALL, "C");
     std::string what_arg("test message");
     std::system_error se(static_cast<int>(std::errc::not_a_directory),
                          std::generic_category(), what_arg.c_str());
diff --git a/libcxx/test/std/diagnostics/syserr/syserr.syserr/syserr.syserr.members/ctor_int_error_category_string.pass.cpp b/libcxx/test/std/diagnostics/syserr/syserr.syserr/syserr.syserr.members/ctor_int_error_category_string.pass.cpp
--- a/libcxx/test/std/diagnostics/syserr/syserr.syserr/syserr.syserr.members/ctor_int_error_category_string.pass.cpp
+++ b/libcxx/test/std/diagnostics/syserr/syserr.syserr/syserr.syserr.members/ctor_int_error_category_string.pass.cpp
@@ -17,11 +17,13 @@
 #include <system_error>
 #include <string>
 #include <cassert>
+#include <clocale>
 
 #include "test_macros.h"
 
 int main(int, char**)
 {
+    std::setlocale (LC_ALL, "C");
     std::string what_arg("test message");
     std::system_error se(static_cast<int>(std::errc::not_a_directory),
                          std::generic_category(), what_arg);