diff --git a/tqtinterface/qt4/src/tools/tqvaluevector.h b/tqtinterface/qt4/src/tools/tqvaluevector.h
index 03ef9d2..be4106f 100644
--- a/tqtinterface/qt4/src/tools/tqvaluevector.h
+++ b/tqtinterface/qt4/src/tools/tqvaluevector.h
@@ -39,6 +39,8 @@
 #ifndef TQVALUEVECTOR_H
 #define TQVALUEVECTOR_H
 
+#include <cstddef>
+
 #ifndef TQT_H
 #include "tqtl.h"
 #include "tqshared.h"