diff --git a/thin-provisioning/emitter.h b/thin-provisioning/emitter.h
index bb944da..83a0397 100644
--- a/thin-provisioning/emitter.h
+++ b/thin-provisioning/emitter.h
@@ -21,6 +21,8 @@
 
 #include <boost/shared_ptr.hpp>
 #include <boost/optional.hpp>
+#include <boost/optional/optional_io.hpp>
+
 #include <string>
 #include <stdint.h>