diff --git a/java/google/registry/model/eppcommon/ProtocolDefinition.java b/java/google/registry/model/eppcommon/ProtocolDefinition.java
index a6b2dd351..cc1fb9933 100644
--- a/java/google/registry/model/eppcommon/ProtocolDefinition.java
+++ b/java/google/registry/model/eppcommon/ProtocolDefinition.java
@@ -35,7 +35,6 @@ import google.registry.model.domain.secdns.SecDnsCreateExtension;
 import google.registry.model.eppinput.EppInput.CommandExtension;
 import google.registry.model.eppoutput.EppResponse.ResponseExtension;
 import java.util.EnumSet;
-import java.util.Set;
 import javax.xml.bind.annotation.XmlSchema;
 
 /** Constants that define the EPP protocol version we support. */
@@ -44,10 +43,11 @@ public class ProtocolDefinition {
 
   public static final String LANGUAGE = "en";
 
-  public static final Set<String> SUPPORTED_OBJECT_SERVICES = ImmutableSet.of(
-      "urn:ietf:params:xml:ns:host-1.0",
-      "urn:ietf:params:xml:ns:domain-1.0",
-      "urn:ietf:params:xml:ns:contact-1.0");
+  public static final ImmutableSet<String> SUPPORTED_OBJECT_SERVICES =
+      ImmutableSet.of(
+          "urn:ietf:params:xml:ns:host-1.0",
+          "urn:ietf:params:xml:ns:domain-1.0",
+          "urn:ietf:params:xml:ns:contact-1.0");
 
   /** Enums repesenting valid service extensions that are recognized by the server. */
   public enum ServiceExtension {
diff --git a/java/google/registry/model/index/ForeignKeyIndex.java b/java/google/registry/model/index/ForeignKeyIndex.java
index 2af0647a0..231f71464 100644
--- a/java/google/registry/model/index/ForeignKeyIndex.java
+++ b/java/google/registry/model/index/ForeignKeyIndex.java
@@ -62,9 +62,9 @@ public abstract class ForeignKeyIndex<E extends EppResource> extends BackupGroup
   @Entity
   public static class ForeignKeyHostIndex extends ForeignKeyIndex<HostResource> {}
 
-  private static final Map<
-      Class<? extends EppResource>,
-      Class<? extends ForeignKeyIndex<?>>> RESOURCE_CLASS_TO_FKI_CLASS =
+  private static final ImmutableMap<
+          Class<? extends EppResource>, Class<? extends ForeignKeyIndex<?>>>
+      RESOURCE_CLASS_TO_FKI_CLASS =
           ImmutableMap.<Class<? extends EppResource>, Class<? extends ForeignKeyIndex<?>>>of(
               ContactResource.class, ForeignKeyContactIndex.class,
               DomainResource.class, ForeignKeyDomainIndex.class,
diff --git a/java/google/registry/rde/RdeUploadUrl.java b/java/google/registry/rde/RdeUploadUrl.java
index f52cb54e4..855ea8e95 100644
--- a/java/google/registry/rde/RdeUploadUrl.java
+++ b/java/google/registry/rde/RdeUploadUrl.java
@@ -23,7 +23,6 @@ import com.google.common.collect.ImmutableMap;
 import java.io.UnsupportedEncodingException;
 import java.net.URI;
 import java.net.URLEncoder;
-import java.util.Map;
 import java.util.Objects;
 import javax.annotation.Nullable;
 import javax.annotation.concurrent.Immutable;
@@ -41,7 +40,8 @@ import javax.annotation.concurrent.Immutable;
 final class RdeUploadUrl implements Comparable<RdeUploadUrl> {
 
   public static final Protocol SFTP = new Protocol("sftp", 22);
-  private static final Map<String, Protocol> ALLOWED_PROTOCOLS = ImmutableMap.of("sftp", SFTP);
+  private static final ImmutableMap<String, Protocol> ALLOWED_PROTOCOLS =
+      ImmutableMap.of("sftp", SFTP);
 
   private final Protocol protocol;
   private final URI uri;
diff --git a/javatests/google/registry/tools/server/KillAllEppResourcesActionTest.java b/javatests/google/registry/tools/server/KillAllEppResourcesActionTest.java
index ca1550fe8..013ed4aee 100644
--- a/javatests/google/registry/tools/server/KillAllEppResourcesActionTest.java
+++ b/javatests/google/registry/tools/server/KillAllEppResourcesActionTest.java
@@ -34,6 +34,7 @@ import static java.util.Arrays.asList;
 import com.google.appengine.api.datastore.Entity;
 import com.google.common.collect.FluentIterable;
 import com.google.common.collect.ImmutableMultimap;
+import com.google.common.collect.ImmutableSet;
 import com.google.common.collect.Iterables;
 import com.googlecode.objectify.Key;
 import google.registry.model.EppResource;
@@ -52,7 +53,6 @@ import google.registry.model.poll.PollMessage;
 import google.registry.model.reporting.HistoryEntry;
 import google.registry.testing.FakeResponse;
 import google.registry.testing.mapreduce.MapreduceTestCase;
-import java.util.Set;
 import org.joda.money.CurrencyUnit;
 import org.joda.money.Money;
 import org.junit.Test;
@@ -63,22 +63,23 @@ import org.junit.runners.JUnit4;
 @RunWith(JUnit4.class)
 public class KillAllEppResourcesActionTest extends MapreduceTestCase<KillAllEppResourcesAction> {
 
-  static final Set<String> AFFECTED_KINDS = FluentIterable
-      .from(asList(
-          EppResourceIndex.class,
-          ForeignKeyContactIndex.class,
-          ForeignKeyDomainIndex.class,
-          ForeignKeyHostIndex.class,
-          DomainApplicationIndex.class,
-          DomainBase.class,
-          ContactResource.class,
-          HostResource.class,
-          HistoryEntry.class,
-          PollMessage.class,
-          BillingEvent.OneTime.class,
-          BillingEvent.Recurring.class))
-      .transform(CLASS_TO_KIND_FUNCTION)
-      .toSet();
+  static final ImmutableSet<String> AFFECTED_KINDS =
+      FluentIterable.from(
+              asList(
+                  EppResourceIndex.class,
+                  ForeignKeyContactIndex.class,
+                  ForeignKeyDomainIndex.class,
+                  ForeignKeyHostIndex.class,
+                  DomainApplicationIndex.class,
+                  DomainBase.class,
+                  ContactResource.class,
+                  HostResource.class,
+                  HistoryEntry.class,
+                  PollMessage.class,
+                  BillingEvent.OneTime.class,
+                  BillingEvent.Recurring.class))
+          .transform(CLASS_TO_KIND_FUNCTION)
+          .toSet();
 
   private void runMapreduce() throws Exception {
     action = new KillAllEppResourcesAction();