A method performed in a source gateway logically positioned in a first wireless access network between a radio device and a first mobility anchor. The source gateway comprises an MTCP proxy for a TCP flow between the device and a peer comprising at least two subflows between the device and the source gateway, including a first subflow over the first network and a second subflow over a second wireless access network. The method comprises receiving uplink data of the second subflow from a second gateway logically positioned in the second network between the device and a second mobility anchor, sending downlink data of the second subflow to said second gateway, moving the proxy from the source gateway to a target gateway logically positioned in the first network between the device and the first mobility anchor, as part of a handover of the radio device, forwarding downlink data to the target gateway, and forwarding the received uplink data of the second subflow to the target gateway.