diff --git a/src/main/java/com/googlesource/gerrit/plugins/replication/Destination.java b/src/main/java/com/googlesource/gerrit/plugins/replication/Destination.java
index 008e50b..98170ae 100644
--- a/src/main/java/com/googlesource/gerrit/plugins/replication/Destination.java
+++ b/src/main/java/com/googlesource/gerrit/plugins/replication/Destination.java
@@ -127,8 +127,8 @@
   }
 
   public static class QueueInfo {
-    public final Map<URIish, PushOne> pending;
-    public final Map<URIish, PushOne> inFlight;
+    public final ImmutableMap<URIish, PushOne> pending;
+    public final ImmutableMap<URIish, PushOne> inFlight;
 
     public QueueInfo(Map<URIish, PushOne> pending, Map<URIish, PushOne> inFlight) {
       this.pending = ImmutableMap.copyOf(pending);
@@ -640,7 +640,7 @@
     }
 
     // by default push all projects
-    List<String> projects = config.getProjects();
+    ImmutableList<String> projects = config.getProjects();
     if (projects.isEmpty()) {
       return true;
     }
diff --git a/src/main/java/com/googlesource/gerrit/plugins/replication/DestinationsCollection.java b/src/main/java/com/googlesource/gerrit/plugins/replication/DestinationsCollection.java
index 08f3477..3854801 100644
--- a/src/main/java/com/googlesource/gerrit/plugins/replication/DestinationsCollection.java
+++ b/src/main/java/com/googlesource/gerrit/plugins/replication/DestinationsCollection.java
@@ -52,7 +52,7 @@
 
   private final Destination.Factory destinationFactory;
   private final Provider<ReplicationQueue> replicationQueue;
-  private volatile List<Destination> destinations;
+  private volatile ImmutableList<Destination> destinations;
   private boolean shuttingDown;
 
   public static class EventQueueNotEmptyException extends Exception {
@@ -258,7 +258,7 @@
     }
   }
 
-  private List<Destination> allDestinations(
+  private ImmutableList<Destination> allDestinations(
       Destination.Factory destinationFactory, List<RemoteConfiguration> remoteConfigurations) {
 
     ImmutableList.Builder<Destination> dest = ImmutableList.builder();
diff --git a/src/main/java/com/googlesource/gerrit/plugins/replication/PushOne.java b/src/main/java/com/googlesource/gerrit/plugins/replication/PushOne.java
index ed84087..54f4463 100644
--- a/src/main/java/com/googlesource/gerrit/plugins/replication/PushOne.java
+++ b/src/main/java/com/googlesource/gerrit/plugins/replication/PushOne.java
@@ -355,7 +355,7 @@
   }
 
   ReplicationState[] getStatesByRef(String ref) {
-    Collection<ReplicationState> states = stateMap.get(ref);
+    List<ReplicationState> states = stateMap.get(ref);
     return states.toArray(new ReplicationState[states.size()]);
   }
 
diff --git a/src/main/java/com/googlesource/gerrit/plugins/replication/RemoteConfiguration.java b/src/main/java/com/googlesource/gerrit/plugins/replication/RemoteConfiguration.java
index 05b4066..726bcf5 100644
--- a/src/main/java/com/googlesource/gerrit/plugins/replication/RemoteConfiguration.java
+++ b/src/main/java/com/googlesource/gerrit/plugins/replication/RemoteConfiguration.java
@@ -14,7 +14,6 @@
 package com.googlesource.gerrit.plugins.replication;
 
 import com.google.common.collect.ImmutableList;
-import java.util.List;
 import org.eclipse.jgit.transport.RemoteConfig;
 
 /** Remote configuration for a replication endpoint */
@@ -117,7 +116,7 @@
    * @return true, when configuration is for a single project, false otherwise
    */
   default boolean isSingleProjectMatch() {
-    List<String> projects = getProjects();
+    ImmutableList<String> projects = getProjects();
     boolean ret = (projects.size() == 1);
     if (ret) {
       String projectMatch = projects.get(0);