diff --git a/src/main/java/com/googlesource/gerrit/plugins/remotegerritaccountcache/AccountCacheImpl.java b/src/main/java/com/googlesource/gerrit/plugins/remotegerritaccountcache/AccountCacheImpl.java
index 0413dde..1d6589f 100644
--- a/src/main/java/com/googlesource/gerrit/plugins/remotegerritaccountcache/AccountCacheImpl.java
+++ b/src/main/java/com/googlesource/gerrit/plugins/remotegerritaccountcache/AccountCacheImpl.java
@@ -69,7 +69,6 @@
 import java.util.Collection;
 import java.util.Collections;
 import java.util.List;
-import java.util.Map;
 import java.util.Optional;
 import java.util.Set;
 import java.util.concurrent.ExecutionException;
@@ -180,7 +179,7 @@
   }
 
   @Override
-  public Map<Account.Id, AccountState> get(Set<Account.Id> accountIds) {
+  public ImmutableMap<Account.Id, AccountState> get(Collection<Account.Id> accountIds) {
     try {
       try (Repository allUsers = repoManager.openRepository(allUsersName)) {
         Set<CachedAccountDetails.Key> keys =