diff --git a/tests/unit-tests/ca-module.t.cpp b/tests/unit-tests/ca-module.t.cpp
index 14b72b2..9fcee0f 100644
--- a/tests/unit-tests/ca-module.t.cpp
+++ b/tests/unit-tests/ca-module.t.cpp
@@ -1,6 +1,6 @@
 /* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
 /*
- * Copyright (c) 2017-2023, Regents of the University of California.
+ * Copyright (c) 2017-2024, Regents of the University of California.
  *
  * This file is part of ndncert, a certificate management system based on NDN.
  *
@@ -19,8 +19,6 @@
  */
 
 #include "ca-module.hpp"
-#include "challenge/challenge-module.hpp"
-#include "challenge/challenge-email.hpp"
 #include "challenge/challenge-pin.hpp"
 #include "detail/info-encoder.hpp"
 #include "requester-request.hpp"
@@ -29,6 +27,7 @@
 #include "tests/io-key-chain-fixture.hpp"
 
 #include <ndn-cxx/metadata-object.hpp>
+#include <ndn-cxx/security/signing-helpers.hpp>
 #include <ndn-cxx/security/verification-helpers.hpp>
 #include <ndn-cxx/util/dummy-client-face.hpp>