diff --git a/synapse/handlers/federation.py b/synapse/handlers/federation.py
index 4e8ffa8f7..7622962d4 100644
--- a/synapse/handlers/federation.py
+++ b/synapse/handlers/federation.py
@@ -688,6 +688,8 @@ class FederationHandler(BaseHandler):
             logger.warn("Failed to create join %r because %s", event, e)
             raise e
 
+        # The remote hasn't signed it yet, obviously. We'll do the full checks
+        # when we get the event back in `on_send_join_request`
         self.auth.check(event, auth_events=context.current_state, do_sig_check=False)
 
         defer.returnValue(event)
@@ -918,6 +920,8 @@ class FederationHandler(BaseHandler):
         )
 
         try:
+            # The remote hasn't signed it yet, obviously. We'll do the full checks
+            # when we get the event back in `on_send_leave_request`
             self.auth.check(event, auth_events=context.current_state, do_sig_check=False)
         except AuthError as e:
             logger.warn("Failed to create new leave %r because %s", event, e)
diff --git a/synapse/state.py b/synapse/state.py
index d7d08570c..ef1bc470b 100644
--- a/synapse/state.py
+++ b/synapse/state.py
@@ -379,6 +379,7 @@ class StateHandler(object):
             try:
                 # FIXME: hs.get_auth() is bad style, but we need to do it to
                 # get around circular deps.
+                # The signatures have already been checked at this point
                 self.hs.get_auth().check(event, auth_events, do_sig_check=False)
                 prev_event = event
             except AuthError:
@@ -391,6 +392,7 @@ class StateHandler(object):
             try:
                 # FIXME: hs.get_auth() is bad style, but we need to do it to
                 # get around circular deps.
+                # The signatures have already been checked at this point
                 self.hs.get_auth().check(event, auth_events, do_sig_check=False)
                 return event
             except AuthError: