diff --git a/ChangeLog b/ChangeLog
index 98a8b2dc54..631f352cd3 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+Thu Nov  3 23:53:04 2011  NAKAMURA Usaku  <usa@ruby-lang.org>
+
+	* encoding.c (rb_locale_charmap): ignore calling nl_langinfo_codeset()
+	  on Windows except cygwin. [experimental]
+
 Thu Nov  3 22:45:09 2011  Tanaka Akira  <akr@fsij.org>
 
 	* ext/socket/socket.c (rsock_socketpair0): extracted from
diff --git a/encoding.c b/encoding.c
index 3e4892b2e2..0aac1f1509 100644
--- a/encoding.c
+++ b/encoding.c
@@ -1446,9 +1446,12 @@ rb_locale_charmap(VALUE klass)
 #if defined NO_LOCALE_CHARMAP
     return rb_usascii_str_new2("ASCII-8BIT");
 #elif defined _WIN32 || defined __CYGWIN__
-    const char *nl_langinfo_codeset(void);
-    const char *codeset = nl_langinfo_codeset();
+    const char *codeset = 0;
     char cp[sizeof(int) * 3 + 4];
+# ifdef __CYGWIN__
+    const char *nl_langinfo_codeset(void);
+    codeset = nl_langinfo_codeset();
+# endif
     if (!codeset) {
 	UINT codepage = GetConsoleCP();
 	if(!codepage) codepage = GetACP();