Methods, systems, and devices for wireless communications are described. A first user equipment (UE) may transmit a control message indicating reservation of a first resource of a sidelink channel for a sidelink transmission. The first UE may receive a pre-conflict indication for the first resource based on the control message. In some cases, the first UE may disregard the pre-conflict indication, or may not disregard the conflict indication based on one or more factors. The first UE may perform resource re-selection to select a second resource for the sidelink transmission if the first UE receives the conflict indication at least a threshold amount of time prior to the first resource, and may transmit using the second resource. Otherwise, the first UE may report a negative acknowledgement (NACK) message from a physical (PHY) layer to a medium access control (MAC) layer.