diff --git a/event/common.go b/event/common.go
index 9825b96..7616359 100644
--- a/event/common.go
+++ b/event/common.go
@@ -94,6 +94,12 @@ const (
 	// RemotePeer: The peer associated with the acknowledgement
 	PeerAcknowledgement = Type("PeerAcknowledgement")
 
+	// Like PeerAcknowledgement but with message index instead of event ID
+	// attributes
+	// Index: The original index of the message that the peer is responding too.
+	// RemotePeer: The peer associated with the acknowledgement
+	IndexedAcknowledgement = Type("IndexedAcknowledgement")
+
 	// attributes:
 	// RemotePeer: [eg "chpr7qm6op5vfcg2pi4vllco3h6aa7exexc4rqwnlupqhoogx2zgd6qd"]
 	// Error: string describing the error
@@ -265,6 +271,7 @@ const (
 	Status       = Field("Status")
 	EventID      = Field("EventID")
 	EventContext = Field("EventContext")
+	Index        = Field("Index")
 
 	Authorization = Field("Authorization")
 
diff --git a/model/profile.go b/model/profile.go
index 983644c..9fe29ec 100644
--- a/model/profile.go
+++ b/model/profile.go
@@ -197,7 +197,7 @@ func (p *Profile) ErrorSentMessageToPeer(onion string, eventID string, error str
 }
 
 // AckSentMessageToPeer sets mesage to a peer as acknowledged
-func (p *Profile) AckSentMessageToPeer(onion string, eventID string) {
+func (p *Profile) AckSentMessageToPeer(onion string, eventID string) int {
 	p.lock.Lock()
 	defer p.lock.Unlock()
 
@@ -207,8 +207,11 @@ func (p *Profile) AckSentMessageToPeer(onion string, eventID string) {
 		if ok {
 			contact.Timeline.Messages[mIdx].Acknowledged = true
 			delete(contact.UnacknowledgedMessages, eventID)
+			return mIdx
 		}
 	}
+
+	return -1
 }
 
 // AddGroupSentMessageError searches matching groups for the message by sig and marks it as an error
diff --git a/peer/cwtch_peer.go b/peer/cwtch_peer.go
index f136b87..342f22c 100644
--- a/peer/cwtch_peer.go
+++ b/peer/cwtch_peer.go
@@ -715,7 +715,10 @@ func (cp *cwtchPeer) eventHandler() {
 
 		case event.PeerAcknowledgement:
 			cp.mutex.Lock()
-			cp.Profile.AckSentMessageToPeer(ev.Data[event.RemotePeer], ev.Data[event.EventID])
+			idx := cp.Profile.AckSentMessageToPeer(ev.Data[event.RemotePeer], ev.Data[event.EventID])
+			edata := ev.Data
+			edata[event.Index] = strconv.Itoa(idx)
+			cp.eventBus.Publish(event.NewEvent(event.IndexedAcknowledgement, edata))
 			cp.mutex.Unlock()
 
 		case event.SendMessageToGroupError: