diff --git a/lib/connect.c b/lib/connect.c
index d52baad..fd4c97b 100644
--- a/lib/connect.c
+++ b/lib/connect.c
@@ -282,7 +282,9 @@ try_again:
 		pdu->itt   = iscsi_itt_post_increment(iscsi);
 		iscsi_pdu_set_itt(pdu, pdu->itt);
 
-		pdu->cmdsn = iscsi->cmdsn++;
+		/* do not increase cmdsn for PDUs marked for immediate delivery
+		 * this will result in a protocol error */
+		pdu->cmdsn = (pdu->outdata.data[0] & ISCSI_PDU_IMMEDIATE)?iscsi->cmdsn:iscsi->cmdsn++;
 		iscsi_pdu_set_cmdsn(pdu, pdu->cmdsn);
 
 		iscsi_pdu_set_expstatsn(pdu, iscsi->statsn);
@@ -312,7 +314,9 @@ try_again:
 		pdu->itt   = iscsi_itt_post_increment(iscsi);
 		iscsi_pdu_set_itt(pdu, pdu->itt);
 
-		pdu->cmdsn = iscsi->cmdsn++;
+		/* do not increase cmdsn for PDUs marked for immediate delivery
+		 * this will result in a protocol error */
+		pdu->cmdsn = (pdu->outdata.data[0] & ISCSI_PDU_IMMEDIATE)?iscsi->cmdsn:iscsi->cmdsn++;
 		iscsi_pdu_set_cmdsn(pdu, pdu->cmdsn);
 
 		iscsi_pdu_set_expstatsn(pdu, iscsi->statsn);
diff --git a/lib/nop.c b/lib/nop.c
index 325013a..3f930c0 100644
--- a/lib/nop.c
+++ b/lib/nop.c
@@ -64,10 +64,12 @@ iscsi_nop_out_async(struct iscsi_context *iscsi, iscsi_command_cb cb,
 	pdu->callback     = cb;
 	pdu->private_data = private_data;
 
-	if (iscsi_pdu_add_data(iscsi, pdu, data, len) != 0) {
-		iscsi_set_error(iscsi, "Failed to add outdata to nop-out");
-		iscsi_free_pdu(iscsi, pdu);
-		return -1;
+	if (data != NULL && len > 0) {
+		if (iscsi_pdu_add_data(iscsi, pdu, data, len) != 0) {
+			iscsi_set_error(iscsi, "Failed to add outdata to nop-out");
+			iscsi_free_pdu(iscsi, pdu);
+			return -1;
+		}
 	}
 
 	if (iscsi_queue_pdu(iscsi, pdu) != 0) {