diff --git a/ChangeLog b/ChangeLog
index 0a9dc4f8d0b5..7f9563afa536 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -7,6 +7,9 @@ Bugfix
      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.
+   * Fix an unsafe bounds check when restoring an SSL session from a ticket.
+     This could lead to a buffer overflow, but only in case ticket authentication
+     was broken. Reported and fix suggested by Guido Vranken in #659.
 
 Changes
    * Add tests for session resumption in DTLS.
diff --git a/library/ssl_ticket.c b/library/ssl_ticket.c
index ad2d5264546e..555c7b63bf95 100644
--- a/library/ssl_ticket.c
+++ b/library/ssl_ticket.c
@@ -192,9 +192,9 @@ static int ssl_save_session( const mbedtls_ssl_session *session,
     if( left < 3 + cert_len )
         return( MBEDTLS_ERR_SSL_BUFFER_TOO_SMALL );
 
-    *p++ = (unsigned char)( cert_len >> 16 & 0xFF );
-    *p++ = (unsigned char)( cert_len >>  8 & 0xFF );
-    *p++ = (unsigned char)( cert_len       & 0xFF );
+    *p++ = (unsigned char)( ( cert_len >> 16 ) & 0xFF );
+    *p++ = (unsigned char)( ( cert_len >>  8 ) & 0xFF );
+    *p++ = (unsigned char)( ( cert_len       ) & 0xFF );
 
     if( session->peer_cert != NULL )
         memcpy( p, session->peer_cert->raw.p, cert_len );
@@ -219,14 +219,14 @@ static int ssl_load_session( mbedtls_ssl_session *session,
     size_t cert_len;
 #endif /* MBEDTLS_X509_CRT_PARSE_C */
 
-    if( p + sizeof( mbedtls_ssl_session ) > end )
+    if( sizeof( mbedtls_ssl_session ) > (size_t)( end - p ) )
         return( MBEDTLS_ERR_SSL_BAD_INPUT_DATA );
 
     memcpy( session, p, sizeof( mbedtls_ssl_session ) );
     p += sizeof( mbedtls_ssl_session );
 
 #if defined(MBEDTLS_X509_CRT_PARSE_C)
-    if( p + 3 > end )
+    if( 3 > (size_t)( end - p ) )
         return( MBEDTLS_ERR_SSL_BAD_INPUT_DATA );
 
     cert_len = ( p[0] << 16 ) | ( p[1] << 8 ) | p[2];
@@ -240,7 +240,7 @@ static int ssl_load_session( mbedtls_ssl_session *session,
     {
         int ret;
 
-        if( p + cert_len > end )
+        if( cert_len > (size_t)( end - p ) )
             return( MBEDTLS_ERR_SSL_BAD_INPUT_DATA );
 
         session->peer_cert = mbedtls_calloc( 1, sizeof( mbedtls_x509_crt ) );
@@ -251,7 +251,7 @@ static int ssl_load_session( mbedtls_ssl_session *session,
         mbedtls_x509_crt_init( session->peer_cert );
 
         if( ( ret = mbedtls_x509_crt_parse_der( session->peer_cert,
-                                        p, cert_len ) ) != 0 )
+                                                p, cert_len ) ) != 0 )
         {
             mbedtls_x509_crt_free( session->peer_cert );
             mbedtls_free( session->peer_cert );