Index: dll/win32/kernel32/winnls/string/nls.c
===================================================================
--- dll/win32/kernel32/winnls/string/nls.c	(revision 57528)
+++ dll/win32/kernel32/winnls/string/nls.c	(working copy)
@@ -359,7 +359,7 @@
     WCHAR WideChar;
     LONG Count;
 
-    if (Flags != 0)
+    if (Flags != 0 && Flags != MB_ERR_INVALID_CHARS)
     {
         SetLastError(ERROR_INVALID_FLAGS);
         return 0;