Index: source/lib/scoped_locale.h
===================================================================
--- /dev/null
+++ source/lib/scoped_locale.h
@@ -0,0 +1,43 @@
+/* Copyright (C) 2019 Wildfire Games.
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining
+ * a copy of this software and associated documentation files (the
+ * "Software"), to deal in the Software without restriction, including
+ * without limitation the rights to use, copy, modify, merge, publish,
+ * distribute, sublicense, and/or sell copies of the Software, and to
+ * permit persons to whom the Software is furnished to do so, subject to
+ * the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included
+ * in all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+ * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+ * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
+ * IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
+ * CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
+ * TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
+ * SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+
+#ifndef INCLUDED_SCOPED_LOCALE
+#define INCLUDED_SCOPED_LOCALE
+
+class ScopedLocale
+{
+public:
+    ScopedLocale(int category, char* newLocale) : m_Category(category)
+    {
+    	m_OldLocale = setlocale(category, NULL);
+        TS_ASSERT(setlocale(m_Category, newLocale) != nullptr);
+    }
+    ~ScopedLocale()
+    {
+        TS_ASSERT(setlocale(m_Category, m_OldLocale));
+    }
+private:
+    int m_Category;
+    char* m_OldLocale;
+};
+
+#endif	// #ifndef INCLUDED_SCOPED_LOCALE
Index: source/ps/tests/test_CStr.h
===================================================================
--- source/ps/tests/test_CStr.h
+++ source/ps/tests/test_CStr.h
@@ -16,6 +16,7 @@
  */
 
 #include "lib/self_test.h"
+#include "lib/scoped_locale.h"
 
 #include "ps/CStr.h"
 
@@ -113,7 +114,7 @@
 		// because GTK+ can change the locale when we're running Atlas.
 		// (If the host system doesn't have the locale we're using for this test
 		// then it'll just stick with the default, which is fine)
-		char* old = setlocale(LC_NUMERIC, "fr_FR.UTF-8");
+		ScopedLocale(LC_NUMERIC, "en_US.UTF-8");
 
 		CStr8 str1("1.234");
 		TS_ASSERT_DELTA(str1.ToFloat(), 1.234f, 0.0001f);
@@ -138,7 +139,5 @@
 		TS_ASSERT_EQUALS(str3.ToUInt(), 3u);
 		TS_ASSERT_EQUALS(str3.ToLong(), 3);
 		TS_ASSERT_EQUALS(str3.ToULong(), 3u);
-
-		setlocale(LC_NUMERIC, old);
 	}
 };
Index: source/ps/tests/test_cppformat.h
===================================================================
--- source/ps/tests/test_cppformat.h
+++ source/ps/tests/test_cppformat.h
@@ -16,6 +16,7 @@
  */
 
 #include "lib/self_test.h"
+#include "lib/scoped_locale.h"
 
 #include "third_party/cppformat/format.h"
 
@@ -25,7 +26,7 @@
 	void test_basic()
 	{
 		// Make test behave independent of current host locale
-		char* old = setlocale(LC_ALL, "en_US.UTF-8");
+		ScopedLocale(LC_ALL, "en_US.UTF-8");
 
 		TS_ASSERT_EQUALS(fmt::sprintf("abc"), "abc");
 
@@ -57,7 +58,5 @@
 		TS_ASSERT_EQUALS(fmt::sprintf("T%sT", (const char*)NULL), "T(null)T");
 
 		TS_ASSERT_EQUALS(fmt::sprintf("T%pT", (void*)0x1234), "T0x1234T");
-
-		setlocale(LC_ALL, old);
 	}
 };