diff --git a/private.h b/private.h
index 3ccb531..658d8d4 100644
--- a/private.h
+++ b/private.h
@@ -190,10 +190,21 @@ extern int	unlink P((const char * filename));
 ** But some newer errno.h implementations define it as a macro.
 ** Fix the former without affecting the latter.
 */
+
 #ifndef errno
 extern int errno;
 #endif /* !defined errno */
 
+/*
+** Some time.h implementations don't declare asctime_r.
+** Others might define it as a macro.
+** Fix the former without affecting the latter.
+*/
+
+#ifndef asctime_r
+extern char *	asctime_r();
+#endif
+
 /*
 ** Private function declarations.
 */