diff --git a/synapse/federation/send_queue.py b/synapse/federation/send_queue.py
index a12c18f4df..7e52a55eda 100644
--- a/synapse/federation/send_queue.py
+++ b/synapse/federation/send_queue.py
@@ -55,17 +55,17 @@ class FederationRemoteSendQueue(object):
         self.notifier = hs.get_notifier()
         self.is_mine_id = hs.is_mine_id
 
-        self.presence_map = {}
-        self.presence_changed = sorteddict()
+        self.presence_map = {}  # Pending presence map user_id -> UserPresenceState
+        self.presence_changed = sorteddict()  # Stream position -> user_id
 
-        self.keyed_edu = {}
-        self.keyed_edu_changed = sorteddict()
+        self.keyed_edu = {}  # (destination, key) -> EDU
+        self.keyed_edu_changed = sorteddict()  # stream position -> (destination, key)
 
-        self.edus = sorteddict()
+        self.edus = sorteddict()  # stream position -> Edu
 
-        self.failures = sorteddict()
+        self.failures = sorteddict()  # stream position -> (destination, Failure)
 
-        self.device_messages = sorteddict()
+        self.device_messages = sorteddict()  # stream position -> destination
 
         self.pos = 1
         self.pos_time = sorteddict()
diff --git a/synapse/handlers/presence.py b/synapse/handlers/presence.py
index 685373ff28..98e736be5b 100644
--- a/synapse/handlers/presence.py
+++ b/synapse/handlers/presence.py
@@ -666,7 +666,7 @@ class PresenceHandler(object):
         """Sends state updates to remote servers.
 
         Args:
-            hosts_to_states (list): list(state)
+            hosts_to_states (list(UserPresenceState))
         """
         self.federation.send_presence(states)
 
@@ -1332,6 +1332,8 @@ def get_interested_remotes(store, states):
         each row the list of UserPresenceState should be sent to each
         destination
     """
+    hosts_and_states = []  # Final result to return
+
     # First we look up the rooms each user is in (as well as any explicit
     # subscriptions), then for each distinct room we look up the remote
     # hosts in those rooms.
@@ -1348,7 +1350,6 @@ def get_interested_remotes(store, states):
         for u in plist:
             users_to_states.setdefault(u, []).append(state)
 
-    hosts_and_states = []
     for room_id, states in room_ids_to_states.items():
         if not local_states:
             continue