diff --git a/marketplace/examples/echo-paper.rkt b/marketplace/examples/echo-paper.rkt
index a0f5974..6317bac 100644
--- a/marketplace/examples/echo-paper.rkt
+++ b/marketplace/examples/echo-paper.rkt
@@ -1,6 +1,6 @@
 #lang marketplace
 
-(subscribe-to-topic (tcp-channel ? (tcp-listener 5999) ?)
+(observe-publishers (tcp-channel ? (tcp-listener 5999) ?)
   (match-conversation (tcp-channel from to _)
     (on-presence (spawn (echoer from to)))))