diff --git a/time/time.h b/time/time.h
index 5a7f419905..e255db9772 100644
--- a/time/time.h
+++ b/time/time.h
@@ -141,7 +141,7 @@ extern char *asctime (const struct tm *__tp) __THROW;
 /* Equivalent to `asctime (localtime (timer))'.  */
 extern char *ctime (const time_t *__timer) __THROW;
 
-#if defined __USE_POSIX || __GLIBC_USE (ISOC2X)
+#ifdef __USE_POSIX
 /* Reentrant versions of the above functions.  */
 
 /* Return in BUF a string of the form "Day Mon dd hh:mm:ss yyyy\n"
@@ -152,7 +152,7 @@ extern char *asctime_r (const struct tm *__restrict __tp,
 /* Equivalent to `asctime_r (localtime_r (timer, *TMP*), buf)'.  */
 extern char *ctime_r (const time_t *__restrict __timer,
 		      char *__restrict __buf) __THROW;
-#endif	/* POSIX || C2X */
+#endif	/* POSIX */
 
 
 /* Defined in localtime.c.  */