diff --git a/Source/build.h b/Source/build.h
index d610afae..2a9db775 100644
--- a/Source/build.h
+++ b/Source/build.h
@@ -325,7 +325,7 @@ class CEXEBuild {
      * return aPS_ERROR.  If this function call is overwriting a set user string,
      * this will return a PS_WARNING.
      */
-    int SetLangString(TCHAR *name, LANGID lang, TCHAR *str, BOOL unicode);
+    int SetLangString(TCHAR *name, LANGID lang, const TCHAR *str, BOOL unicode);
 
     /**
      * Sets the user string to the specific NLF_STRINGS id.
diff --git a/Source/lang.cpp b/Source/lang.cpp
index 09f513c7..f120573c 100644
--- a/Source/lang.cpp
+++ b/Source/lang.cpp
@@ -473,7 +473,7 @@ int CEXEBuild::DefineInnerLangString(int id, int process/*=-1*/) {
 // @return If the language id, the variable name or string is invalid, it will
 // return a PS_ERROR.  If this function call is overwriting a set user string,
 // this will return a PS_WARNING.
-int CEXEBuild::SetLangString(TCHAR *name, LANGID lang, TCHAR *str, BOOL unicode) {
+int CEXEBuild::SetLangString(TCHAR *name, LANGID lang, const TCHAR *str, BOOL unicode) {
   if (!str || !name) return PS_ERROR;
 
   LanguageTable *table = GetLangTable(lang);