diff --git a/squinnondation/messages.py b/squinnondation/messages.py
index a0da0fa..db270b4 100644
--- a/squinnondation/messages.py
+++ b/squinnondation/messages.py
@@ -213,7 +213,7 @@ class DataTLV(TLV):
             return
 
         # Acknowledge the packet
-        squirrel.send_packet(sender, Packet.construct(AckTLV.construct(sender.id, self.nonce)))
+        squirrel.send_packet(sender, Packet.construct(AckTLV.construct(self.sender_id, self.nonce)))
 
         nickname_match = re.match("(.*): (.*)", msg)
         if nickname_match is None: