diff --git a/asterix-common/src/main/java/edu/uci/ics/asterix/common/context/PrimaryIndexOperationTracker.java b/asterix-common/src/main/java/edu/uci/ics/asterix/common/context/PrimaryIndexOperationTracker.java
index 69dba5e..7304b4f 100644
--- a/asterix-common/src/main/java/edu/uci/ics/asterix/common/context/PrimaryIndexOperationTracker.java
+++ b/asterix-common/src/main/java/edu/uci/ics/asterix/common/context/PrimaryIndexOperationTracker.java
@@ -31,7 +31,7 @@
 public class PrimaryIndexOperationTracker extends BaseOperationTracker {
 
     // Number of active operations on a ILSMIndex instance.
-    private AtomicInteger numActiveOperations;
+    private final AtomicInteger numActiveOperations;
 
     public PrimaryIndexOperationTracker(DatasetLifecycleManager datasetLifecycleManager, int datasetID,
             ILSMIOOperationCallbackFactory ioOpCallbackFactory) {