FortiOS 6.0.3: KeepAlive not found

After upgrading from 5.4.x to 6.0.3 I am not able set keepalive enable on phase2 anymore.

I have compared the old and new configuration, and the VPN-config is the same (expect the keepalive-config).

Any idé why it is gone and any alternative commands?

Best regards

Yngve

config vpn ipsec phase1-interface
    edit "VPN_ABC01"
        set type ddns
        set interface "wan1"
        set ike-version 2
        set peertype any
        set proposal aes128-sha1
        set dpd on-idle
        set remotegw-ddns "abc01.mydomain.net"
        set psksecret ENC secret
        set dpd-retryinterval 5
    next
end

config vpn ipsec phase2-interface
    edit "VPN_ABC01"
        set phase1name "VPN_ABC01"
        set proposal aes128-sha1
        set auto-negotiate enable
    next
end