diff --git a/linux/wpa-controller/WpaController.cxx b/linux/wpa-controller/WpaController.cxx
index dd88a459..9205e5c4 100644
--- a/linux/wpa-controller/WpaController.cxx
+++ b/linux/wpa-controller/WpaController.cxx
@@ -1,4 +1,5 @@
 
+#include <cstddef>
 #include <wpa_ctrl.h>
 #include <Wpa/WpaController.hxx>