diff --git a/src/viewport_gui.cpp b/src/viewport_gui.cpp
--- a/src/viewport_gui.cpp
+++ b/src/viewport_gui.cpp
@@ -28,6 +28,7 @@ static const NWidgetPart _nested_extra_v
 		NWidget(WWT_CLOSEBOX, COLOUR_GREY),
 		NWidget(WWT_CAPTION, COLOUR_GREY, WID_EV_CAPTION), SetDataTip(STR_EXTRA_VIEW_PORT_TITLE, STR_TOOLTIP_WINDOW_TITLE_DRAG_THIS),
 		NWidget(WWT_SHADEBOX, COLOUR_GREY),
+		NWidget(WWT_DEFSIZEBOX, COLOUR_GREY),
 		NWidget(WWT_STICKYBOX, COLOUR_GREY),
 	EndContainer(),
 	NWidget(WWT_PANEL, COLOUR_GREY),