diff --git a/shell/ActivitiesModel.py b/shell/ActivitiesModel.py
index dfff1608..c46256d2 100644
--- a/shell/ActivitiesModel.py
+++ b/shell/ActivitiesModel.py
@@ -30,20 +30,31 @@ class ActivitiesModel(gobject.GObject):
 	def __init__(self, registry):
 		gobject.GObject.__init__(self)
 		
-		self._activities = []
+		self._activities = {}
 		self._registry = registry
 		
 		self._pservice = PresenceService()
 		self._pservice.connect("service-appeared", self.__service_appeared_cb)
 
+		for service in self._pservice.get_services():
+			self.__check_service(service)
+
+	def has_activity(self, activity_id):
+		return self._activities.has_key(activity_id)
+
 	def add_activity(self, service):
 		activity_info = ActivityInfo(service)
-		self._activities.append(activity_info)
+		self._activities[activity_info.get_id()] = (activity_info)
 		self.emit('activity-added', activity_info)
 
 	def __iter__(self):
-		return self._activities.__iter__()
+		activities = self._activities.values()
+		return activities.__iter__()
 
 	def __service_appeared_cb(self, pservice, service):
+		self.__check_service(service)
+
+	def __check_service(self, service):
 		if self._registry.get_activity(service.get_type()) != None:
-			self.add_activity(service)
+			if not self.has_activity(service.get_activity_id()):
+				self.add_activity(service)
diff --git a/sugar/activity/Activity.py b/sugar/activity/Activity.py
index ce036e9e..c1e9297a 100644
--- a/sugar/activity/Activity.py
+++ b/sugar/activity/Activity.py
@@ -1,4 +1,5 @@
 import sys
+import logging
 
 import dbus
 import dbus.service
@@ -116,7 +117,7 @@ class ActivityDbusService(dbus.service.Object):
 
 	@dbus.service.method(ACTIVITY_SERVICE_NAME)
 	def get_shared(self):
-		"""Get the activity identifier"""
+		"""Returns True if the activity is shared on the mesh."""
 		return self._activity.get_shared()
 
 class Activity(gtk.Window):
@@ -165,10 +166,23 @@ class Activity(gtk.Window):
 		return self._activity_id
 
 	def join(self, activity_ps):
-		"""Join an activity shared on the network"""
+		"""Join an activity shared on the network."""
 		self._shared = True
 		self._activity_id = activity_ps.get_id()
 
+		# Publish the default service, it's a copy of
+		# one of those we found on the network.
+		services = activity_ps.get_services_of_type(self._default_type)
+		if len(services) > 0:
+			service = services[0]
+			addr = service.get_address()
+			port = service.get_port()
+			properties = { 'title' : service.get_published_value('title') }
+			self._service = self._pservice.share_activity(self,
+								self._default_type, properties, addr, port)
+		else:
+			logging.error('Cannot join the activity')
+
 	def share(self):
 		"""Share the activity on the network."""
 		properties = { 'title' : self.get_title() }