diff --git a/ChangeLog b/ChangeLog
index 1a1845e..64dce14 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -5,6 +5,11 @@
 Bugfix
     * Fix failure in hmac_drbg in the benchmark sample application, when
       MBEDTLS_THREADING_C is defined. Found by TrinityTonic, #1095
+    * Fix a bug in the update function for SSL ticket keys which previously
+      invalidated keys of a lifetime of less than a 1s. Fixes #1968.
+
+Changes
+   * Add tests for session resumption in DTLS.
 
 = mbed TLS 2.1.15 branch released 2018-08-31
 
diff --git a/library/ssl_ticket.c b/library/ssl_ticket.c
index 0e27900..a27d2ec 100644
--- a/library/ssl_ticket.c
+++ b/library/ssl_ticket.c
@@ -101,7 +101,7 @@
         uint32_t current_time = (uint32_t) time( NULL );
         uint32_t key_time = ctx->keys[ctx->active].generation_time;
 
-        if( current_time > key_time &&
+        if( current_time >= key_time &&
             current_time - key_time < ctx->ticket_lifetime )
         {
             return( 0 );
diff --git a/tests/ssl-opt.sh b/tests/ssl-opt.sh
index ec9e75a..34f29ff 100755
--- a/tests/ssl-opt.sh
+++ b/tests/ssl-opt.sh
@@ -1235,6 +1235,71 @@
             -s "session successfully restored from ticket" \
             -s "a session has been resumed"
 
+# Tests for Session Tickets with DTLS
+
+run_test    "Session resume using tickets, DTLS: basic" \
+            "$P_SRV debug_level=3 dtls=1 tickets=1" \
+            "$P_CLI debug_level=3 dtls=1 tickets=1 reconnect=1" \
+            0 \
+            -c "client hello, adding session ticket extension" \
+            -s "found session ticket extension" \
+            -s "server hello, adding session ticket extension" \
+            -c "found session_ticket extension" \
+            -c "parse new session ticket" \
+            -S "session successfully restored from cache" \
+            -s "session successfully restored from ticket" \
+            -s "a session has been resumed" \
+            -c "a session has been resumed"
+
+run_test    "Session resume using tickets, DTLS: cache disabled" \
+            "$P_SRV debug_level=3 dtls=1 tickets=1 cache_max=0" \
+            "$P_CLI debug_level=3 dtls=1 tickets=1 reconnect=1" \
+            0 \
+            -c "client hello, adding session ticket extension" \
+            -s "found session ticket extension" \
+            -s "server hello, adding session ticket extension" \
+            -c "found session_ticket extension" \
+            -c "parse new session ticket" \
+            -S "session successfully restored from cache" \
+            -s "session successfully restored from ticket" \
+            -s "a session has been resumed" \
+            -c "a session has been resumed"
+
+run_test    "Session resume using tickets, DTLS: timeout" \
+            "$P_SRV debug_level=3 dtls=1 tickets=1 cache_max=0 ticket_timeout=1" \
+            "$P_CLI debug_level=3 dtls=1 tickets=1 reconnect=1 reco_delay=2" \
+            0 \
+            -c "client hello, adding session ticket extension" \
+            -s "found session ticket extension" \
+            -s "server hello, adding session ticket extension" \
+            -c "found session_ticket extension" \
+            -c "parse new session ticket" \
+            -S "session successfully restored from cache" \
+            -S "session successfully restored from ticket" \
+            -S "a session has been resumed" \
+            -C "a session has been resumed"
+
+run_test    "Session resume using tickets, DTLS: openssl server" \
+            "$O_SRV -dtls1" \
+            "$P_CLI dtls=1 debug_level=3 tickets=1 reconnect=1" \
+            0 \
+            -c "client hello, adding session ticket extension" \
+            -c "found session_ticket extension" \
+            -c "parse new session ticket" \
+            -c "a session has been resumed"
+
+run_test    "Session resume using tickets, DTLS: openssl client" \
+            "$P_SRV dtls=1 debug_level=3 tickets=1" \
+            "( $O_CLI -dtls1 -sess_out $SESSION; \
+               $O_CLI -dtls1 -sess_in $SESSION; \
+               rm -f $SESSION )" \
+            0 \
+            -s "found session ticket extension" \
+            -s "server hello, adding session ticket extension" \
+            -S "session successfully restored from cache" \
+            -s "session successfully restored from ticket" \
+            -s "a session has been resumed"
+
 # Tests for Session Resume based on session-ID and cache
 
 run_test    "Session resume using cache: tickets enabled on client" \
@@ -1330,6 +1395,101 @@
             -C "parse new session ticket" \
             -c "a session has been resumed"
 
+# Tests for Session Resume based on session-ID and cache, DTLS
+
+run_test    "Session resume using cache, DTLS: tickets enabled on client" \
+            "$P_SRV dtls=1 debug_level=3 tickets=0" \
+            "$P_CLI dtls=1 debug_level=3 tickets=1 reconnect=1" \
+            0 \
+            -c "client hello, adding session ticket extension" \
+            -s "found session ticket extension" \
+            -S "server hello, adding session ticket extension" \
+            -C "found session_ticket extension" \
+            -C "parse new session ticket" \
+            -s "session successfully restored from cache" \
+            -S "session successfully restored from ticket" \
+            -s "a session has been resumed" \
+            -c "a session has been resumed"
+
+run_test    "Session resume using cache, DTLS: tickets enabled on server" \
+            "$P_SRV dtls=1 debug_level=3 tickets=1" \
+            "$P_CLI dtls=1 debug_level=3 tickets=0 reconnect=1" \
+            0 \
+            -C "client hello, adding session ticket extension" \
+            -S "found session ticket extension" \
+            -S "server hello, adding session ticket extension" \
+            -C "found session_ticket extension" \
+            -C "parse new session ticket" \
+            -s "session successfully restored from cache" \
+            -S "session successfully restored from ticket" \
+            -s "a session has been resumed" \
+            -c "a session has been resumed"
+
+run_test    "Session resume using cache, DTLS: cache_max=0" \
+            "$P_SRV dtls=1 debug_level=3 tickets=0 cache_max=0" \
+            "$P_CLI dtls=1 debug_level=3 tickets=0 reconnect=1" \
+            0 \
+            -S "session successfully restored from cache" \
+            -S "session successfully restored from ticket" \
+            -S "a session has been resumed" \
+            -C "a session has been resumed"
+
+run_test    "Session resume using cache, DTLS: cache_max=1" \
+            "$P_SRV dtls=1 debug_level=3 tickets=0 cache_max=1" \
+            "$P_CLI dtls=1 debug_level=3 tickets=0 reconnect=1" \
+            0 \
+            -s "session successfully restored from cache" \
+            -S "session successfully restored from ticket" \
+            -s "a session has been resumed" \
+            -c "a session has been resumed"
+
+run_test    "Session resume using cache, DTLS: timeout > delay" \
+            "$P_SRV dtls=1 debug_level=3 tickets=0" \
+            "$P_CLI dtls=1 debug_level=3 tickets=0 reconnect=1 reco_delay=0" \
+            0 \
+            -s "session successfully restored from cache" \
+            -S "session successfully restored from ticket" \
+            -s "a session has been resumed" \
+            -c "a session has been resumed"
+
+run_test    "Session resume using cache, DTLS: timeout < delay" \
+            "$P_SRV dtls=1 debug_level=3 tickets=0 cache_timeout=1" \
+            "$P_CLI dtls=1 debug_level=3 tickets=0 reconnect=1 reco_delay=2" \
+            0 \
+            -S "session successfully restored from cache" \
+            -S "session successfully restored from ticket" \
+            -S "a session has been resumed" \
+            -C "a session has been resumed"
+
+run_test    "Session resume using cache, DTLS: no timeout" \
+            "$P_SRV dtls=1 debug_level=3 tickets=0 cache_timeout=0" \
+            "$P_CLI dtls=1 debug_level=3 tickets=0 reconnect=1 reco_delay=2" \
+            0 \
+            -s "session successfully restored from cache" \
+            -S "session successfully restored from ticket" \
+            -s "a session has been resumed" \
+            -c "a session has been resumed"
+
+run_test    "Session resume using cache, DTLS: openssl client" \
+            "$P_SRV dtls=1 debug_level=3 tickets=0" \
+            "( $O_CLI -dtls1 -sess_out $SESSION; \
+               $O_CLI -dtls1 -sess_in $SESSION; \
+               rm -f $SESSION )" \
+            0 \
+            -s "found session ticket extension" \
+            -S "server hello, adding session ticket extension" \
+            -s "session successfully restored from cache" \
+            -S "session successfully restored from ticket" \
+            -s "a session has been resumed"
+
+run_test    "Session resume using cache, DTLS: openssl server" \
+            "$O_SRV -dtls1" \
+            "$P_CLI dtls=1 debug_level=3 tickets=0 reconnect=1" \
+            0 \
+            -C "found session_ticket extension" \
+            -C "parse new session ticket" \
+            -c "a session has been resumed"
+
 # Tests for Max Fragment Length extension
 
 MAX_CONTENT_LEN_EXPECT='16384'