diff --git a/src/main.cpp b/src/main.cpp
index 2f90f161d..31becb7d2 100644
--- a/src/main.cpp
+++ b/src/main.cpp
@@ -42,6 +42,7 @@
 #include <boost/math/distributions/poisson.hpp>
 #include <boost/thread.hpp>
 #include <boost/static_assert.hpp>
+#include <boost/optional.hpp>
 
 using namespace std;