diff --git a/include/boost/test/data/size.hpp b/include/boost/test/data/size.hpp
index 3e9ba96795..035bb2e56f 100644
--- a/include/boost/test/data/size.hpp
+++ b/include/boost/test/data/size.hpp
@@ -17,6 +17,7 @@
 
 // STL
 #include <iosfwd>
+#include <cstddef>
 
 #include <boost/test/detail/suppress_warnings.hpp>