diff --git a/index.js b/index.js
index 11e25f87..3199417f 100644
--- a/index.js
+++ b/index.js
@@ -23,3 +23,4 @@ exports.exponentialBuckets =
 exports.collectDefaultMetrics = require('./lib/defaultMetrics');
 
 exports.aggregators = require('./lib/metricAggregators').aggregators;
+exports.AggregatorRegistry = require('./lib/cluster');