diff --git a/scst/src/scst_lib.c b/scst/src/scst_lib.c
index da890b9c3..7c4e858bd 100644
--- a/scst/src/scst_lib.c
+++ b/scst/src/scst_lib.c
@@ -6870,6 +6870,19 @@ out_finish:
 	goto out;
 }
 
+/*
+ * The Data-Out Buffer contains two instances of logical block data:
+ * 1) the compare instance, in which:
+ *   A) the user data is used for the compare operation; and
+ *   B) the protection information, if any, is not used;
+ * and
+ * 2) the write instance, in which:
+ *   A) the user data is used for the write operations; and
+ *   B) the protection information, if any, is used for the write operations.
+ *
+ * Note: cmd->data_len is half of the DataOut buffer size while cmd->bufflen
+ * and cmd->expected_transfer_len refer to the entire DataOut buffer.
+ */
 enum scst_exec_res scst_cmp_wr_local(struct scst_cmd *cmd)
 {
 	enum scst_exec_res res = SCST_EXEC_COMPLETED;
@@ -6913,6 +6926,14 @@ enum scst_exec_res scst_cmp_wr_local(struct scst_cmd *cmd)
 	cwrp->cwr_orig_cmd = cmd;
 	cwrp->cwr_finish_fn = scst_cwr_read_cmd_finished;
 
+	if (cmd->bufflen != scst_cmd_get_expected_transfer_len_data(cmd)) {
+		PRINT_ERROR("COMPARE AND WRITE: data buffer length mismatch (CDB %u <> ini %u)",
+			    cmd->bufflen,
+			    scst_cmd_get_expected_transfer_len_data(cmd));
+		scst_set_invalid_field_in_cdb(cmd, 13/*NLB*/, 0);
+		goto out_done;
+	}
+
 	/*
 	 * As required by SBC, DIF PI, if any, is not checked for the read part
 	 */