diff --git a/include/mbedtls/ssl_ticket.h b/include/mbedtls/ssl_ticket.h
index 201849e..80dcd2b 100644
--- a/include/mbedtls/ssl_ticket.h
+++ b/include/mbedtls/ssl_ticket.h
@@ -52,6 +52,7 @@
 typedef struct
 {
     mbedtls_ssl_ticket_key keys[2]; /*!< ticket protection keys             */
+    unsigned char active;           /*!< index of the currently active key  */
 
     uint32_t ticket_lifetime;       /*!< lifetime of tickets in seconds     */