Unscheduled transmissions of one wireless network device while a collocated wireless network device has control of a communication medium can corrupt packets received by the collocated wireless network device. Interference between the collocated wireless network devices can lead to degradation in performance of either/both the wireless network devices. In a communication system comprising a first wireless network device collocated with a second wireless network device, the first wireless network device can be configured to transmit a coexistence message to the second wireless network device when the first wireless network device transmits a packet without control of the communication medium. On receiving the coexistence message indicating that the first wireless network device transmitted a packet without control of the communication medium, the second wireless network device can discard any packets received at the second wireless network device and can request retransmission of the discarded packets.