diff --git a/docs/content/docs.md b/docs/content/docs.md
index 2de1c664f..fdaa7b0d3 100644
--- a/docs/content/docs.md
+++ b/docs/content/docs.md
@@ -464,6 +464,9 @@ transfers as soon as possible.
 This flag can be useful on IO limited systems where transfers
 interfere with checking.
 
+It can also be useful to ensure perfect ordering when using
+`--order-by`.
+
 Using this flag can use more memory as it effectively sets
 `--max-backlog` to infinite. This means that all the info on the
 objects to transfer is held in memory before the transfers start.
@@ -1071,6 +1074,10 @@ Rclone will do its best to transfer the best file it has so in
 practice this should not cause a problem.  Think of `--order-by` as
 being more of a best efforts flag rather than a perfect ordering.
 
+If you want perfect ordering then you will need to specify
+[--check-first](#check-first) which will find all the files which need
+transferring first before transferring any.
+
 ### --password-command SpaceSepList ###
 
 This flag supplies a program which should supply the config password