diff --git a/extent.cpp b/extent.cpp
index 6f64e4bb..7e1c3eb0 100644
--- a/extent.cpp
+++ b/extent.cpp
@@ -20,7 +20,8 @@
 #include "./maths.hpp"
 #include "./stream.hpp"
 
-#include <cmath>
+#include <algorithm>
+#include <numeric>
 
 using util::extent;
 using util::extent_range;