diff --git a/src/main/java/com/googlesource/gerrit/plugins/replication/ReplicationMetrics.java b/src/main/java/com/googlesource/gerrit/plugins/replication/ReplicationMetrics.java
index e02084d..a7b27a0 100644
--- a/src/main/java/com/googlesource/gerrit/plugins/replication/ReplicationMetrics.java
+++ b/src/main/java/com/googlesource/gerrit/plugins/replication/ReplicationMetrics.java
@@ -24,9 +24,9 @@
 
 @Singleton
 public class ReplicationMetrics {
-  Timer1<String> executionTime;
-  Histogram1<String> executionDelay;
-  Histogram1<String> executionRetries;
+  private final Timer1<String> executionTime;
+  private final Histogram1<String> executionDelay;
+  private final Histogram1<String> executionRetries;
 
   @Inject
   ReplicationMetrics(MetricMaker metricMaker) {