Index: include/libgen.h
===================================================================
--- include/libgen.h
+++ include/libgen.h
@@ -52,7 +52,7 @@
  */
 #if defined(__generic) && !defined(__cplusplus)
 __BEGIN_DECLS
-char	*__old_dirname(const char *);
+char	*__old_dirname(char *);
 __END_DECLS
 __sym_compat(dirname, __old_dirname, FBSD_1.0);
 #define	dirname(x)	__generic(x, const char *, __old_dirname, dirname)(x)