diff --git a/javatests/com/google/gerrit/elasticsearch/ElasticV6QueryChangesTest.java b/javatests/com/google/gerrit/elasticsearch/ElasticV6QueryChangesTest.java
index e840fb9..68c4b71 100644
--- a/javatests/com/google/gerrit/elasticsearch/ElasticV6QueryChangesTest.java
+++ b/javatests/com/google/gerrit/elasticsearch/ElasticV6QueryChangesTest.java
@@ -57,6 +57,8 @@
 
   @After
   public void closeIndex() {
+    // Close the index after each test to prevent exceeding Elasticsearch's
+    // shard limit (see Issue 10120).
     client.execute(
         new HttpPost(
             String.format(
diff --git a/javatests/com/google/gerrit/elasticsearch/ElasticV7QueryChangesTest.java b/javatests/com/google/gerrit/elasticsearch/ElasticV7QueryChangesTest.java
index 0cfdbfc..b61bc72 100644
--- a/javatests/com/google/gerrit/elasticsearch/ElasticV7QueryChangesTest.java
+++ b/javatests/com/google/gerrit/elasticsearch/ElasticV7QueryChangesTest.java
@@ -57,6 +57,8 @@
 
   @After
   public void closeIndex() {
+    // Close the index after each test to prevent exceeding Elasticsearch's
+    // shard limit (see Issue 10120).
     client.execute(
         new HttpPost(
             String.format(