EventEmitter constructor was not being called in many places. It did work due to the EventEmitter3 constructor being empty, but we can't rely on that.

lib/util/ttlset.js

@@ -10,6 +10,7 @@ function TtlItem(value) {
 }
 
 function TtlSet(ttl) {
+  EventEmitter.call(this)
   this.head = null
   this.tail = null
   this.mapping = Object.create(null)