--- a/unix/unxcfg.h
+++ b/unix/unxcfg.h
@@ -117,7 +117,7 @@ typedef struct stat z_stat;
 #  endif
 #else
 #  include <time.h>
-   struct tm *gmtime(), *localtime();
+   struct tm *gmtime(const time_t *), *localtime(const time_t *);
 #endif
 
 #if (defined(BSD4_4) || (defined(SYSV) && defined(MODERN)))