diff --git a/cpp/graph-inl.h b/cpp/graph-inl.h
index 8808911ba..fb2a197c3 100644
--- a/cpp/graph-inl.h
+++ b/cpp/graph-inl.h
@@ -12,6 +12,8 @@
 #include <boost/graph/graph_traits.hpp>
 #include <boost/graph/adjacency_list.hpp>
 #include <boost/graph/breadth_first_search.hpp>
+#include <boost/shared_ptr.hpp>
+
 
 using namespace std;