#else /* HAVE_UNSETENV */
# undef unsetenv
+# if !HAVE_DECL_UNSETENV
+# if VOID_UNSETENV
+extern void unsetenv (const char *);
+# else
+extern int unsetenv (const char *);
+# endif
+# endif
/* Call the underlying unsetenv, in case there is hidden bookkeeping
that needs updating beyond just modifying environ. */