diff --git a/include/xo/facet/OObject.hpp b/include/xo/facet/OObject.hpp
index 0a92a4a..93b532d 100644
--- a/include/xo/facet/OObject.hpp
+++ b/include/xo/facet/OObject.hpp
@@ -9,6 +9,7 @@
 #include "typeseq.hpp"
 #include <new>
 #include <cstring>
+#include <cstddef>
 
 namespace xo {
     namespace facet {