3 files changed, 3 insertions, 3 deletions
diff --git a/synapse/http/__init__.py b/synapse/http/__init__.py
index 3880ce0d94..8eb3638591 100644
--- a/synapse/http/__init__.py
+++ b/synapse/http/__init__.py
@@ -27,7 +27,7 @@ class RequestTimedOutError(SynapseError):
     """Exception representing timeout of an outbound request"""
 
     def __init__(self):
-        super(RequestTimedOutError, self).__init__(504, "Timed out")
+        super().__init__(504, "Timed out")
 
 
 def cancelled_to_request_timed_out_error(value, timeout):
diff --git a/synapse/http/federation/well_known_resolver.py b/synapse/http/federation/well_known_resolver.py
index e6f067ca29..a306faa267 100644
--- a/synapse/http/federation/well_known_resolver.py
+++ b/synapse/http/federation/well_known_resolver.py
@@ -311,7 +311,7 @@ def _parse_cache_control(headers: Headers) -> Dict[bytes, Optional[bytes]]:
     return cache_controls
 
 
-@attr.s()
+@attr.s(slots=True)
 class _FetchWellKnownFailure(Exception):
     # True if we didn't get a non-5xx HTTP response, i.e. this may or may not be
     # a temporary failure.
diff --git a/synapse/http/matrixfederationclient.py b/synapse/http/matrixfederationclient.py
index 5eaf3151ce..3c86cbc546 100644
--- a/synapse/http/matrixfederationclient.py
+++ b/synapse/http/matrixfederationclient.py
@@ -76,7 +76,7 @@ MAXINT = sys.maxsize
 _next_id = 1
 
 
-@attr.s(frozen=True)
+@attr.s(slots=True, frozen=True)
 class MatrixFederationRequest:
     method = attr.ib()
     """HTTP method