diff --git a/content/docs/rfcs/16/README.md b/content/docs/rfcs/16/README.md
index 1adf306c..9a229cfe 100644
--- a/content/docs/rfcs/16/README.md
+++ b/content/docs/rfcs/16/README.md
@@ -107,6 +107,8 @@ The following structured types are defined for use on the Relay API:
 | ----: | :---: | :---: | ----------- |
 | `payload` | `String` | mandatory | The payload being relayed as a hex encoded data string |
 | `contentTopic` | `String` | optional | Message content topic for optional content-based filtering |
+| `timestamp` | `Number` | optional | The time at which the message is generated by its sender. This field holds the Unix epoch time in seconds as a 64-bits float value. The fractional part represents sub-seconds.  |
+
 
  > **_NOTE:_** `WakuRelayMessage` maps directly to a [`WakuMessage`](#WakuMessage), except that the latter contains an explicit message `version`. For `WakuRelay` purposes, the versioning is handled by the API.