diff --git a/Source/kwsys/SystemTools.cxx b/Source/kwsys/SystemTools.cxx
index 93cc5b3dd..b68a9bfa8 100644
--- a/Source/kwsys/SystemTools.cxx
+++ b/Source/kwsys/SystemTools.cxx
@@ -836,7 +836,14 @@ kwsys_stl::string SystemTools::CapitalizedWords(const kwsys_stl::string& s)
   kwsys_stl::string n(s);
   for (size_t i = 0; i < s.size(); i++)
     {
+#if defined(_MSC_VER) && defined (_MT) && defined (_DEBUG)
+    // MS has an assert that will fail if s[i] < 0; setting
+    // LC_CTYPE using setlocale() does *not* help. Painful.
+    if ((int)s[i] >= 0 && isalpha(s[i]) && 
+        (i == 0 || ((int)s[i - 1] >= 0 && isspace(s[i - 1]))))
+#else
     if (isalpha(s[i]) && (i == 0 || isspace(s[i - 1])))
+#endif        
       {
       n[i] = static_cast<kwsys_stl::string::value_type>(toupper(s[i]));
       }
@@ -850,7 +857,14 @@ kwsys_stl::string SystemTools::UnCapitalizedWords(const kwsys_stl::string& s)
   kwsys_stl::string n(s);
   for (size_t i = 0; i < s.size(); i++)
     {
+#if defined(_MSC_VER) && defined (_MT) && defined (_DEBUG)
+    // MS has an assert that will fail if s[i] < 0; setting
+    // LC_CTYPE using setlocale() does *not* help. Painful.
+    if ((int)s[i] >= 0 && isalpha(s[i]) && 
+        (i == 0 || ((int)s[i - 1] >= 0 && isspace(s[i - 1]))))
+#else
     if (isalpha(s[i]) && (i == 0 || isspace(s[i - 1])))
+#endif        
       {
       n[i] = static_cast<kwsys_stl::string::value_type>(tolower(s[i]));
       }