diff --git a/src/main/java/com/googlesource/gerrit/plugins/reviewers/PutReviewers.java b/src/main/java/com/googlesource/gerrit/plugins/reviewers/PutReviewers.java
index 04fd051..5f55db2 100644
--- a/src/main/java/com/googlesource/gerrit/plugins/reviewers/PutReviewers.java
+++ b/src/main/java/com/googlesource/gerrit/plugins/reviewers/PutReviewers.java
@@ -51,7 +51,7 @@
 class PutReviewers implements RestModifyView<ProjectResource, Input> {
   private static final FluentLogger logger = FluentLogger.forEnclosingClass();
 
-  public static class Input {
+  protected static class Input {
     public Action action;
     public String filter;
     public String reviewer;