diff --git a/src/github.com/matrix-org/dendrite/roomserver/api/output.go b/src/github.com/matrix-org/dendrite/roomserver/api/output.go
index f1b402315..f84ed7766 100644
--- a/src/github.com/matrix-org/dendrite/roomserver/api/output.go
+++ b/src/github.com/matrix-org/dendrite/roomserver/api/output.go
@@ -98,3 +98,28 @@ type OutputNewRoomEvent struct {
 	// future proof the API for virtual hosting.
 	SendAsServer string `json:"send_as_server"`
 }
+
+// An OutputNewInviteEvent is written whenever an invite becomes active.
+// Invite events can be received outside of an existing room so have to be
+// tracked separately from the room events themselves.
+type OutputNewInviteEvent struct {
+	// The "m.room.member" invite event.
+	Event gomatrixserverlib.Event `json:"event"`
+}
+
+// An OutputRetireInviteEvent is written whenever an existing invite is no longer
+// active. An invite stops being active if the user joins the room or if the
+// invite is rejected by the user.
+type OutputRetireInviteEvent struct {
+	// The room ID of the "m.room.member" invite event.
+	RoomID string
+	// The ID of the "m.room.member" invite event.
+	EventID string
+	// Optional event ID of the event that replaced the invite.
+	// This can be empty if the invite was rejected locally and we were unable
+	// to reach the server that originally sent the invite.
+	ReplacedByEventID string
+	// The "membership" of the user after retiring the invite. One of "join"
+	// "leave" or "ban".
+	Membership string
+}
diff --git a/src/github.com/matrix-org/dendrite/roomserver/input/membership.go b/src/github.com/matrix-org/dendrite/roomserver/input/membership.go
index 9ed655216..575230d9c 100644
--- a/src/github.com/matrix-org/dendrite/roomserver/input/membership.go
+++ b/src/github.com/matrix-org/dendrite/roomserver/input/membership.go
@@ -50,7 +50,7 @@ func updateMemberships(
 		}
 		if change.added.EventNID != 0 {
 			ev, _ := eventMap(events).lookup(change.added.EventNID)
-			if ae != nil {
+			if ev != nil {
 				ae = &ev.Event
 			}
 			targetNID = change.added.EventStateKeyNID