diff --git a/src/util/random.hpp b/src/util/random.hpp
index 075d5aa72..d6405dfac 100644
--- a/src/util/random.hpp
+++ b/src/util/random.hpp
@@ -3,6 +3,7 @@
 #include <random>
 #include <string>
 #include <algorithm>
+#include <functional>
 
 namespace util {
     template <