diff --git a/Tle.cpp b/Tle.cpp
index e1500d3..aa25d7a 100644
--- a/Tle.cpp
+++ b/Tle.cpp
@@ -351,7 +351,7 @@ void Tle::ValidateLine(const std::string& line, const std::string& pattern)
                 /*
                  * number or ' '
                  */
-                if (!isdigit(mtch) && mtch != ' ')
+                if (!std::isdigit(mtch, std::locale::classic()) && mtch != ' ')
                 {
                     throw TleException("Invalid character");
                 }
@@ -364,7 +364,7 @@ void Tle::ValidateLine(const std::string& line, const std::string& pattern)
                  */
                 if (mtch != '+' && mtch != '-'
                         && mtch != ' ' && mtch != '0'
-                        && !isdigit(mtch))
+                        && !std::isdigit(mtch, std::locale::classic()))
                 {
                     throw TleException("Invalid character");
                 }
@@ -397,7 +397,9 @@ void Tle::ValidateLine(const std::string& line, const std::string& pattern)
                 /*
                  * alpha or ' '
                  */
-                if (!isupper(mtch) && !isalpha(mtch) && mtch != ' ')
+                if (!std::isupper(mtch, std::locale::classic()) &&
+                        !std::isalpha(mtch, std::locale::classic()) &&
+                        mtch != ' ')
                 {
                     throw TleException("Invalid character");
                 }
@@ -424,7 +426,7 @@ int Tle::CheckSum(const std::string & str)
     {
         char ch = str[i];
 
-        if (isdigit(ch))
+        if (std::isdigit(ch, std::locale::classic()))
         {
             xsum += (ch - '0');
         }
diff --git a/Util.cpp b/Util.cpp
index eed94c2..2dc1ff5 100644
--- a/Util.cpp
+++ b/Util.cpp
@@ -1,28 +1,38 @@
-#include "Util.h"
-
-#include <algorithm>
-#include <locale>
-
-namespace Util
-{
-    void TrimLeft(std::string& s)
-    {
-        s.erase(s.begin(),
-                std::find_if(s.begin(), s.end(),
-                    std::not1(std::ptr_fun<int, int>(std::isspace))));
-    }
-
-    void TrimRight(std::string& s)
-    {
-        s.erase(std::find_if(s.rbegin(), s.rend(),
-                std::not1(std::ptr_fun<int, int>(std::isspace))).base(),
-                s.end());
-    }
-
-    void Trim(std::string& s)
-    {
-        TrimLeft(s);
-        TrimRight(s);
-    }
-
-}
+#include "Util.h"
+
+#include <algorithm>
+#include <locale>
+#include <functional>
+
+namespace Util
+{
+    namespace
+    {
+        struct IsDigit: std::unary_function<char, bool>
+        {
+            bool operator()(char c) const
+            {
+                return std::isdigit(c, std::locale::classic()) == 0;
+            }
+        };
+    }
+
+    void TrimLeft(std::string& s)
+    {
+        s.erase(s.begin(),
+                std::find_if(s.begin(), s.end(), std::not1(IsDigit())));
+    }
+
+    void TrimRight(std::string& s)
+    {
+        s.erase(std::find_if(s.rbegin(), s.rend(), std::not1(IsDigit())).base(),
+                s.end());
+    }
+
+    void Trim(std::string& s)
+    {
+        TrimLeft(s);
+        TrimRight(s);
+    }
+
+}