diff --git a/lib/api/middlewares/pubsub-metrics.js b/lib/api/middlewares/pubsub-metrics.js
index ae0195d4..8ef538a8 100644
--- a/lib/api/middlewares/pubsub-metrics.js
+++ b/lib/api/middlewares/pubsub-metrics.js
@@ -64,6 +64,7 @@ function normalizedField (field) {
     return field.toString().trim().substr(0, MAX_LENGTH);
 }
 
+// FIXME: 'X-Tiler-Profiler' might not be accurate enough
 function getResponseTime (res) {
     const profiler = res.get('X-Tiler-Profiler');
     let stats;