diff --git a/src/vroom_write.cc b/src/vroom_write.cc
index 9cc7d954..e399acee 100644
--- a/src/vroom_write.cc
+++ b/src/vroom_write.cc
@@ -1,5 +1,6 @@
 #include "grisu3.h"
 #include <array>
+#include <functional>
 #include <future>
 #include <iterator>