1 files changed, 2 insertions, 1 deletions
diff --git a/synapse/util/caches/lrucache.py b/synapse/util/caches/lrucache.py
index 4bc1a67b58..33eae2b7c4 100644
--- a/synapse/util/caches/lrucache.py
+++ b/synapse/util/caches/lrucache.py
@@ -64,7 +64,8 @@ class LruCache:
         Args:
             max_size: The maximum amount of entries the cache can hold
 
-            keylen: The length of the tuple used as the cache key
+            keylen: The length of the tuple used as the cache key. Ignored unless
+                cache_type is `TreeCache`.
 
             cache_type (type):
                 type of underlying cache to be used. Typically one of dict