--- portage/portage/interpolate/interpolate_1st_order.h.orig	2019-06-19 13:52:51.930855056 -0600
+++ portage/portage/interpolate/interpolate_1st_order.h	2019-06-19 13:53:05.087946460 -0600
@@ -13,6 +13,7 @@
 #include <iostream>
 #include <utility>
 #include <vector>
+#include <math.h>
 
 #include "portage/support/portage.h"