diff --git a/src/changes.C b/src/changes.C
index 133c5b76aa..53d89e494e 100644
--- a/src/changes.C
+++ b/src/changes.C
@@ -16,6 +16,7 @@
 #include "changes.h"
 #include "debug.h"
 
+#include <cmath>
 #include <boost/assert.hpp>