diff --git a/synapse/util/caches/__init__.py b/synapse/util/caches/__init__.py
index b675da44dd..4b8a0c7a8f 100644
--- a/synapse/util/caches/__init__.py
+++ b/synapse/util/caches/__init__.py
@@ -118,9 +118,6 @@ def register_cache(
             resize_callback = getattr(cache, "set_cache_factor")
         add_resizable_cache(cache_name, resize_callback)
 
-    # Check if the metric is already registered. Unregister it, if so.
-    # This usually happens during tests, as at runtime these caches are
-    # effectively singletons.
     metric = CacheMetric(cache, cache_type, cache_name, collect_callback)
     metric_name = "cache_%s_%s" % (cache_type, cache_name)
     caches_by_name[cache_name] = cache