diff --git a/docs/content/b2.md b/docs/content/b2.md
index e15e4413e..edfe8bd79 100644
--- a/docs/content/b2.md
+++ b/docs/content/b2.md
@@ -117,6 +117,12 @@ the following characters are also replaced:
 Invalid UTF-8 bytes will also be [replaced](/overview/#invalid-utf8),
 as they can't be used in JSON strings.
 
+Note that in 2020-05 Backblaze started allowing \ characters in file
+names. Rclone hasn't changed its encoding as this could cause syncs to
+re-transfer files. If you want rclone not to replace \ then see the
+`--b2-encoding` flag below and remove the `BackSlash` from the
+string. This can be set in the config.
+
 ### SHA1 checksums ###
 
 The SHA1 checksums of the files are checked on upload and download and