diff --git a/test/power_test.cpp b/test/power_test.cpp
index 20204c1..c1d5c23 100644
--- a/test/power_test.cpp
+++ b/test/power_test.cpp
@@ -8,6 +8,7 @@
 */
 
 #include <iostream>
+#include <functional>
 
 #include <boost/config.hpp>
 #include <boost/algorithm/algorithm.hpp>