diff --git a/scst/src/scst_lib.c b/scst/src/scst_lib.c
index 69e442e12..edf9d3e97 100644
--- a/scst/src/scst_lib.c
+++ b/scst/src/scst_lib.c
@@ -8496,6 +8496,7 @@ int scst_scsi_exec_async(struct scst_cmd *cmd, void *data,
 	}
 
 	if (cmd->data_direction == SCST_DATA_BIDI) {
+#ifdef QUEUE_FLAG_BIDI
 		struct request *next_rq;
 
 		if (!test_bit(QUEUE_FLAG_BIDI, &q->queue_flags)) {
@@ -8518,6 +8519,9 @@ int scst_scsi_exec_async(struct scst_cmd *cmd, void *data,
 			goto out_free_unmap;
 		}
 		rq->next_rq = next_rq;
+#else
+		return -EOPNOTSUPP;
+#endif
 	} else {
 		rq = blk_map_kern_sg(q, cmd->sg, cmd->sg_cnt, gfp, reading);
 		if (IS_ERR(rq)) {
@@ -8558,6 +8562,7 @@ int scst_scsi_exec_async(struct scst_cmd *cmd, void *data,
 out:
 	return res;
 
+#ifdef QUEUE_FLAG_BIDI
 out_free_unmap:
 	{
 	struct bio *bio = rq->bio, *b;
@@ -8580,6 +8585,7 @@ out_free_unmap:
 	rq->bio = NULL;
 
 	blk_put_request(rq);
+#endif
 
 out_free_sioc:
 	kmem_cache_free(scsi_io_context_cache, sioc);
diff --git a/scst_local/scst_local.c b/scst_local/scst_local.c
index 1be668940..92e584247 100644
--- a/scst_local/scst_local.c
+++ b/scst_local/scst_local.c
@@ -1076,7 +1076,8 @@ static int scst_local_queuecommand_lck(struct scsi_cmnd *scmd,
 #endif
 
 	if (scsi_bidi_cmnd(scmd)) {
-#if LINUX_VERSION_CODE > KERNEL_VERSION(2, 6, 24)
+#if LINUX_VERSION_CODE > KERNEL_VERSION(2, 6, 24) && \
+	LINUX_VERSION_CODE < KERNEL_VERSION(5, 1, 0)
 		/* Some of these symbols are only defined after 2.6.24 */
 		dir = SCST_DATA_BIDI;
 		scst_cmd_set_expected(scst_cmd, dir, scsi_bufflen(scmd));
@@ -1243,7 +1244,7 @@ static int scst_local_slave_alloc(struct scsi_device *sdev)
 #if !defined(RHEL_MAJOR) || RHEL_MAJOR -0 >= 6
 	queue_flag_set_unlocked(QUEUE_FLAG_BIDI, sdev->request_queue);
 #endif
-#else
+#elif LINUX_VERSION_CODE < KERNEL_VERSION(5, 1, 0)
 	blk_queue_flag_set(QUEUE_FLAG_BIDI, sdev->request_queue);
 #endif
 
diff --git a/srpt/src/ib_srpt.c b/srpt/src/ib_srpt.c
index 917d9a99f..1f8790fde 100644
--- a/srpt/src/ib_srpt.c
+++ b/srpt/src/ib_srpt.c
@@ -3110,7 +3110,7 @@ static int srpt_map_sg_to_ib_sge(struct srpt_rdma_ch *ch,
 				 struct srpt_send_ioctx *ioctx,
 				 struct scst_cmd *cmd)
 {
-	struct ib_device *dev;
+	struct ib_device *dev __maybe_unused;
 	struct scatterlist *sg, *cur_sg;
 	int sg_cnt;
 	scst_data_direction dir;