A radio base station (RBS), such as an eNodeB, for supporting TTI bundling transmissions from a User Equipment (UE) using is provided. The RBS is arranged for toggling a TTI bundling mode of the UE by transmitting a first signal (531) to the UE, and for receiving a second signal (538) from the UE indicating that the UE has toggled its TTI bundling mode. During the transition state of the switching procedure, between transmitting the first signal and receiving the second signal, all transmissions from the UE are scheduled as TTI bundling transmissions (532, 536), transmissions received from the UE are decoded at time instances for both normal transmissions (511) and TTI bundling transmissions (512), and feedback information is transmitted to the UE at time instances for both normal transmissions (534) and TTI bundling transmissions (535). In this way, all packets received at the RBS may be decoded correctly and retransmission of packets by the UE is avoided. Further, a corresponding method is provided.