Default gateway missing after connection setup

[Jaco]

Binary package hint: network-manager-openvpn

When I setup my OpenVPN connection with user-pass authentication, the server pushes the correct DNS servers. The connection works, except that it doesn't setup the routing table right. The routing table is as follows after connection setup. The default gateway

Destination Gateway Genmask Flags Metric Ref Use Iface
VPN_SERVER 192.168.1.1 255.255.255.255 UGH 0 0 0 eth1
192.168.1.0 * 255.255.255.240 U 0 0 0 eth1
default * 0.0.0.0 U 0 0 0 tap0

My network connection breaks completely since it doesn't have a default gateway anymore. I have to do a
$ sudo route add default gw VPN_SERVER dev tap0
before the network connection works again, routing everything trough the VPN tunnel. This results in the following routing table:

Destination Gateway Genmask Flags Metric Ref Use Iface
VPN_SERVER 192.168.1.1 255.255.255.255 UGH 0 0 0 eth1
192.168.1.0 * 255.255.255.240 U 0 0 0 eth1
default VPN_SERVER 0.0.0.0 UG 0 0 0 tap0
default * 0.0.0.0 U 0 0 0 tap0

This seems to be a bug in n-m-openvpn, it fails to setup the routing table properly.