diff --git a/src/main/java/com/googlesource/gerrit/plugins/cachedrefdb/CachedGitRepositoryManager.java b/src/main/java/com/googlesource/gerrit/plugins/cachedrefdb/CachedGitRepositoryManager.java
index e527725..e3fde24 100644
--- a/src/main/java/com/googlesource/gerrit/plugins/cachedrefdb/CachedGitRepositoryManager.java
+++ b/src/main/java/com/googlesource/gerrit/plugins/cachedrefdb/CachedGitRepositoryManager.java
@@ -21,7 +21,7 @@
 import com.google.inject.Inject;
 import com.google.inject.Singleton;
 import java.io.IOException;
-import java.util.SortedSet;
+import java.util.NavigableSet;
 import org.eclipse.jgit.lib.Repository;
 
 @Singleton
@@ -47,7 +47,7 @@
   }
 
   @Override
-  public SortedSet<Project.NameKey> list() {
+  public NavigableSet<Project.NameKey> list() {
     return repoManager.list();
   }