diff --git a/docs/1.0.md b/docs/1.0.md
index 3efa56c..b9a8cd2 100644
--- a/docs/1.0.md
+++ b/docs/1.0.md
@@ -424,7 +424,7 @@ to allow for file integrity checking.
 
 ### Attributes
  - **type:** (required) Mime type of the media asset.
- - **length:** (required) Length of the file in bytes.
+ - **length:** (recommended) Length of the file in bytes.
  - **bitrate:** (optional) Average encoding bitrate of the media asset, expressed in bits per second.
  - **height:** (optional) Height of the media asset for video formats.
  - **lang:** (optional) An [IETF language tag (BCP 47)](https://en.wikipedia.org/wiki/BCP_47) code identifying the language of this media.