diff --git a/include/wx/sizer.h b/include/wx/sizer.h
index ade5aea748..86550a0e9a 100644
--- a/include/wx/sizer.h
+++ b/include/wx/sizer.h
@@ -21,6 +21,7 @@
 #include "wx/window.h"
 #include "wx/frame.h"
 #include "wx/dialog.h"
+#include "wx/bookctrl.h"
 
 //---------------------------------------------------------------------------
 // classes