diff --git a/streams/src/test/java/org/apache/kafka/streams/integration/RegexSourceIntegrationTest.java b/streams/src/test/java/org/apache/kafka/streams/integration/RegexSourceIntegrationTest.java
index 10e06508b900f..8c00ee4f4829f 100644
--- a/streams/src/test/java/org/apache/kafka/streams/integration/RegexSourceIntegrationTest.java
+++ b/streams/src/test/java/org/apache/kafka/streams/integration/RegexSourceIntegrationTest.java
@@ -318,8 +318,8 @@ public void testMultipleConsumersCanReadFromPartitionedTopic() throws Exception
             partitionedStreamLeader.to(outputTopic, Produced.with(stringSerde, stringSerde));
             partitionedStreamFollower.to(outputTopic, Produced.with(stringSerde, stringSerde));
 
-            final List<String> leaderAssignment = new ArrayList<>();
-            final List<String> followerAssignment = new ArrayList<>();
+            final List<String> leaderAssignment = new CopyOnWriteArrayList<>();
+            final List<String> followerAssignment = new CopyOnWriteArrayList<>();
 
             partitionedStreamsLeader  = new KafkaStreams(builderLeader.build(), streamsConfiguration, new DefaultKafkaClientSupplier() {
                 @Override