diff --git a/java/com/google/gerrit/server/permissions/PermissionBackend.java b/java/com/google/gerrit/server/permissions/PermissionBackend.java
index f0f7f42..a87eb24 100644
--- a/java/com/google/gerrit/server/permissions/PermissionBackend.java
+++ b/java/com/google/gerrit/server/permissions/PermissionBackend.java
@@ -348,7 +348,7 @@
      */
     public Map<String, Ref> filter(List<Ref> refs, Repository repo, RefFilterOptions opts)
         throws PermissionBackendException {
-      return filter(refs.stream().collect(toMap(Ref::getName, r -> r)), repo, opts);
+      return filter(refs.stream().collect(toMap(Ref::getName, r -> r, (a, b) -> b)), repo, opts);
     }
   }
 
diff --git a/java/com/google/gerrit/server/restapi/change/DeleteChangeOp.java b/java/com/google/gerrit/server/restapi/change/DeleteChangeOp.java
index 05de507..80bdd1a 100644
--- a/java/com/google/gerrit/server/restapi/change/DeleteChangeOp.java
+++ b/java/com/google/gerrit/server/restapi/change/DeleteChangeOp.java
@@ -38,8 +38,8 @@
 import org.eclipse.jgit.lib.ObjectId;
 import org.eclipse.jgit.revwalk.RevWalk;
 
-class DeleteChangeOp implements BatchUpdateOp {
-  interface Factory {
+public class DeleteChangeOp implements BatchUpdateOp {
+  public interface Factory {
     DeleteChangeOp create(Change.Id id);
   }