diff --git a/src/common/intl.cpp b/src/common/intl.cpp
index 5e03cbdc18..12beb715c7 100644
--- a/src/common/intl.cpp
+++ b/src/common/intl.cpp
@@ -615,7 +615,12 @@ bool wxLocale::Init(const wxChar *szName,
   if ( m_strShort.IsEmpty() ) {
     // FIXME I don't know how these 2 letter abbreviations are formed,
     //       this wild guess is surely wrong
-    m_strShort = tolower(szLocale[0]) + tolower(szLocale[1]);
+    if ( szLocale[0] )
+    {
+        m_strShort += (wxChar)wxTolower(szLocale[0]);
+        if ( szLocale[1] )
+            m_strShort += (wxChar)wxTolower(szLocale[1]);
+    }
   }
 
   // save the old locale to be able to restore it later