2 files changed, 3 insertions, 4 deletions
diff --git a/synapse/api/constants.py b/synapse/api/constants.py
index 12d18137e0..85001d9676 100644
--- a/synapse/api/constants.py
+++ b/synapse/api/constants.py
@@ -50,7 +50,7 @@ class Membership:
     KNOCK: Final = "knock"
     LEAVE: Final = "leave"
     BAN: Final = "ban"
-    LIST: Final = {INVITE, JOIN, KNOCK, LEAVE, BAN}
+    LIST: Final = frozenset((INVITE, JOIN, KNOCK, LEAVE, BAN))
 
 
 class PresenceState:
diff --git a/synapse/api/ratelimiting.py b/synapse/api/ratelimiting.py
index 26b8711851..b80630c5d3 100644
--- a/synapse/api/ratelimiting.py
+++ b/synapse/api/ratelimiting.py
@@ -236,9 +236,8 @@ class Ratelimiter:
             requester: The requester that is doing the action, if any.
             key: An arbitrary key used to classify an action. Defaults to the
                 requester's user ID.
-            n_actions: The number of times the user wants to do this action. If the user
-                cannot do all of the actions, the user's action count is not incremented
-                at all.
+            n_actions: The number of times the user performed the action. May be negative
+                to "refund" the rate limit.
             _time_now_s: The current time. Optional, defaults to the current time according
                 to self.clock. Only used by tests.
         """