diff --git a/crates/daphne-server/src/metrics.rs b/crates/daphne-server/src/metrics.rs
index a383d468..4df745ee 100644
--- a/crates/daphne-server/src/metrics.rs
+++ b/crates/daphne-server/src/metrics.rs
@@ -80,7 +80,7 @@ mod prometheus {
         }
 
         fn aggregate_job_latency(&self, _time: Duration) {
-            // unimplemented by default
+            // unimplemented by default due to elevated cardinality
         }
     }