diff --git a/synapse/storage/transactions.py b/synapse/storage/transactions.py
index 1c588bd46b..5055c04b24 100644
--- a/synapse/storage/transactions.py
+++ b/synapse/storage/transactions.py
@@ -245,7 +245,7 @@ class TransactionStore(SQLBaseStore):
 
         return self.cursor_to_dict(txn)
 
-    @cached()
+    @cached(max_entries=10000)
     def get_destination_retry_timings(self, destination):
         """Gets the current retry timings (if any) for a given destination.