diff --git a/libc/include/time.h b/libc/include/time.h
index 5251ff3..35c2358 100644
--- a/libc/include/time.h
+++ b/libc/include/time.h
@@ -64,6 +64,7 @@
 #define   TM_ZONE   tm_zone
 
 extern char* asctime(const struct tm* a);
+extern char* asctime_r(const struct tm* a, char* buf);
 
 /* Return the difference between TIME1 and TIME0.  */
 extern double difftime (time_t __time1, time_t __time0);