diff --git a/src/frontends/qt4/LyXToolBox.cpp b/src/frontends/qt4/LyXToolBox.cpp
index fcd3dbeea3..4e754f98ab 100644
--- a/src/frontends/qt4/LyXToolBox.cpp
+++ b/src/frontends/qt4/LyXToolBox.cpp
@@ -9,6 +9,8 @@
  * Full author contact details are available in file CREDITS.
  */
 
+#include <config.h>
+
 #include "LyXToolBox.h"
 
 #include <QApplication>