A wireless device receives a first downlink control information (DCI) comprising a first hybrid automatic request (HARQ) process identifier and a first new data indicator (NDI). A second DCI is received with the first HARQ process identifier and a second NDI. The second NDI is considered as toggled regardless of a value of the second NDI in response to the first DCI indicating postponing a HARQ acknowledgement transmission for a HARQ process identified by the first HARQ process identifier. The wireless device flushes a HARQ buffer associated with the HARQ process based on the second NDI being toggled.