diff --git a/mantis-server/mantis-server-worker/src/main/java/io/mantisrx/server/worker/WorkerIndexHistory.java b/mantis-server/mantis-server-worker/src/main/java/io/mantisrx/server/worker/WorkerIndexHistory.java
index 65fbcc00e..8865d5a52 100644
--- a/mantis-server/mantis-server-worker/src/main/java/io/mantisrx/server/worker/WorkerIndexHistory.java
+++ b/mantis-server/mantis-server-worker/src/main/java/io/mantisrx/server/worker/WorkerIndexHistory.java
@@ -22,8 +22,8 @@
 
 public class WorkerIndexHistory {
 
-    final Set<Integer> runningWorkerIndex = new HashSet<>();
-    final Set<Integer> terminalWorkerIndex = new HashSet<>();
+    private final Set<Integer> runningWorkerIndex = new HashSet<>();
+    private final Set<Integer> terminalWorkerIndex = new HashSet<>();
 
     public synchronized void addToRunningIndex(int workerIndex) {
         runningWorkerIndex.add(workerIndex);