diff --git a/FEDERATION.md b/FEDERATION.md
index f184ac8..88c1f63 100644
--- a/FEDERATION.md
+++ b/FEDERATION.md
@@ -89,7 +89,9 @@ To leave a group, an actor sends a `Undo/Follow/Group` activity to the group inb
 
 ## Group change notifications
 
-When a member joins or leaves a group, an `Update/Collection` activity is created for the group follower's collection and sent to all members of the group. This activity may be throttled to occur less frequently by instance operators.
+When an actor joins a group, a `Join` activity is created for the actor and group and published to all of the group's followers.
+
+When an actor leaves a group, a `Leave` activity is created for the actor and group and published to all of the group's followers.
 
 ## Invitations