1 files changed, 3 insertions, 0 deletions
diff --git a/synapse/util/caches/descriptors.py b/synapse/util/caches/descriptors.py
index 3a20efc566..78ebc485dc 100644
--- a/synapse/util/caches/descriptors.py
+++ b/synapse/util/caches/descriptors.py
@@ -244,6 +244,9 @@ class Cache(object):
 
     def prefill(self, key, value, callback=None):
         callbacks = [callback] if callback else []
+
+        self.ratio_tracking.add(str(hash(key)))
+
         self.cache.set(key, value, callbacks=callbacks)
 
     def invalidate(self, key):