diff --git a/include/langinfo.h b/include/langinfo.h
index 2a81c6ddaf..8f2cb8140c 100644
--- a/include/langinfo.h
+++ b/include/langinfo.h
@@ -1 +1,7 @@
-#include <locale/langinfo.h>
+#ifndef _LANGINFO_H
+# include <locale/langinfo.h>
+
+/* Internal prototypes.  */
+extern char *__nl_langinfo_l (nl_item __item, __locale_t l);
+
+#endif