diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index 447b76c..8d5d9b0 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -7051,6 +7051,11 @@ enum {
 					 * SK_BPF_CB_TX_TIMESTAMPING feature
 					 * is on.
 					 */
+	BPF_SOCK_OPS_TSTAMP_ACK_CB,	/* Called when all the skbs in the
+					 * same sendmsg call are acked
+					 * when SK_BPF_CB_TX_TIMESTAMPING
+					 * feature is on.
+					 */
 };
 
 /* List of TCP states. There is a build check in net/ipv4/tcp.c to detect