diff --git a/src/graphing_calculations.cpp b/src/graphing_calculations.cpp
index 61c4c8a4..dc91edfe 100644
--- a/src/graphing_calculations.cpp
+++ b/src/graphing_calculations.cpp
@@ -7,6 +7,7 @@
 #include <cstring>
 #include <sstream>
 #include <algorithm>
+#include <functional>
 #include "graphing_calculations.h"
 
 #ifdef __WIN32