diff --git a/daemon/main.cpp b/daemon/main.cpp
index 6d29646..60a589a 100644
--- a/daemon/main.cpp
+++ b/daemon/main.cpp
@@ -1,6 +1,6 @@
 /* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
 /*
- * Copyright (c) 2014-2021,  Regents of the University of California,
+ * Copyright (c) 2014-2022,  Regents of the University of California,
  *                           Arizona Board of Regents,
  *                           Colorado State University,
  *                           University Pierre & Marie Curie, Sorbonne University,
@@ -33,6 +33,7 @@
 
 #include <string.h> // for strsignal()
 
+#include <boost/asio/signal_set.hpp>
 #include <boost/config.hpp>
 #include <boost/exception/diagnostic_information.hpp>
 #include <boost/filesystem.hpp>