diff --git a/src/calculator/util/SludgeVolumeIndex.cpp b/src/calculator/util/SludgeVolumeIndex.cpp
index 525b1a32..f575fd95 100644
--- a/src/calculator/util/SludgeVolumeIndex.cpp
+++ b/src/calculator/util/SludgeVolumeIndex.cpp
@@ -1,5 +1,6 @@
 #include <vector>
 #include "calculator/util/SludgeVolumeIndex.h"
+#include <cmath>
 
 using namespace std;