diff --git a/src/main/java/org/elasticsearch/index/fielddata/IndexFieldDataCache.java b/src/main/java/org/elasticsearch/index/fielddata/IndexFieldDataCache.java
index c48652f854e..f7f00f9ddd5 100644
--- a/src/main/java/org/elasticsearch/index/fielddata/IndexFieldDataCache.java
+++ b/src/main/java/org/elasticsearch/index/fielddata/IndexFieldDataCache.java
@@ -151,7 +151,7 @@ public interface IndexFieldDataCache {
 
         static class Key {
             final Object readerKey;
-            final List<Listener> listeners = new ArrayList<>(); // optional stats listener
+            final List<Listener> listeners = new ArrayList<>();
             long sizeInBytes = -1; // optional size in bytes (we keep it here in case the values are soft references)
 
             Key(Object readerKey) {
diff --git a/src/main/java/org/elasticsearch/indices/fielddata/cache/IndicesFieldDataCache.java b/src/main/java/org/elasticsearch/indices/fielddata/cache/IndicesFieldDataCache.java
index 36969833ab7..3c4456ad10e 100644
--- a/src/main/java/org/elasticsearch/indices/fielddata/cache/IndicesFieldDataCache.java
+++ b/src/main/java/org/elasticsearch/indices/fielddata/cache/IndicesFieldDataCache.java
@@ -197,7 +197,7 @@ public class IndicesFieldDataCache extends AbstractComponent implements RemovalL
         public final IndexFieldCache indexCache;
         public final Object readerKey;
 
-        public final List<IndexFieldDataCache.Listener> listeners = new ArrayList<>(); // optional stats listener
+        public final List<IndexFieldDataCache.Listener> listeners = new ArrayList<>();
         long sizeInBytes = -1; // optional size in bytes (we keep it here in case the values are soft references)