diff --git a/include/mbedtls/mbedtls_config.h b/include/mbedtls/mbedtls_config.h
index 19efff7d9..679f7eb86 100644
--- a/include/mbedtls/mbedtls_config.h
+++ b/include/mbedtls/mbedtls_config.h
@@ -1550,9 +1550,21 @@
 //#define MBEDTLS_SSL_TLS1_3_COMPATIBILITY_MODE
 
 /**
- * \def MBEDTLS_SSL_TLS1_3_TICKET_NONCE_LENGTH
+ * \def MBEDTLS_SSL_TLS1_3_TICKET_AGE_TOLERANCE
  *
- * Time in seconds of max ticket lifetime. This is not used in TLS 1.2.
+ * Maximum time difference in milliseconds tolerated between the age of a
+ * ticket from the server and client point of view.
+ * From the client point of view, the age of a ticket is the time difference
+ * between the time when the client proposes to the server to use the ticket
+ * (time of writing of the Pre-Shared Key Extension including the ticket) and
+ * the time the client received the ticket from the server.
+ * From the server point of view, the age of a ticket is the time difference
+ * between the time when the server receives a proposition from the client
+ * to use the ticket and the time when the ticket was created by the server.
+ * The server age is expected to be always greater than the client one and
+ * MBEDTLS_SSL_TLS1_3_TICKET_AGE_TOLERANCE defines the
+ * maximum difference tolerated for the server to accept the ticket.
+ * This is not used in TLS 1.2.
  *
  */
 #define MBEDTLS_SSL_TLS1_3_TICKET_AGE_TOLERANCE 6000