diff --git a/library/ssl_tls13_server.c b/library/ssl_tls13_server.c
index 8076b14..374e1a2 100644
--- a/library/ssl_tls13_server.c
+++ b/library/ssl_tls13_server.c
@@ -229,7 +229,7 @@
      *
      * NOTE: The typical accuracy of an RTC crystal is ±100 to ±20 parts per
      *       million (360 to 72 milliseconds per hour). Default tolerance
-     *       windows is 6s, thus in the worst case client and servers must
+     *       window is 6s, thus in the worst case clients and servers must
      *       sync up their system time every 6000/360/2~=8 hours.
      */
     client_age = obfuscated_ticket_age - session->ticket_age_add;