diff --git a/exercises/gigasecond/gigasecond_test.cpp b/exercises/gigasecond/gigasecond_test.cpp
index 4d2f8b85..6b535d11 100644
--- a/exercises/gigasecond/gigasecond_test.cpp
+++ b/exercises/gigasecond/gigasecond_test.cpp
@@ -1,6 +1,7 @@
 #include "gigasecond.h"
 #define BOOST_TEST_MAIN
 #include <boost/test/unit_test.hpp>
+#include "boost/date_time/posix_time/posix_time.hpp"
 
 // See <http://www.boost.org/doc/libs/1_59_0/doc/html/date_time/posix_time.html>
 // for documentation on boost::posix_time