diff --git a/lib/iscsi-command.c b/lib/iscsi-command.c
index 1164d7b..2385a94 100644
--- a/lib/iscsi-command.c
+++ b/lib/iscsi-command.c
@@ -332,7 +332,7 @@ iscsi_scsi_command_async(struct iscsi_context *iscsi, int lun,
 			len = iscsi->first_burst_length - pdu->payload_len;
 		}
 		iscsi_send_data_out(iscsi, pdu, 0xffffffff,
-				    pdu->payload_len, len);
+				    pdu->payload_len, len - pdu->payload_len);
 	}
 
 	/* remember cmdsn and itt so we can use task management */