diff --git a/src/tree_gui.cpp b/src/tree_gui.cpp
--- a/src/tree_gui.cpp
+++ b/src/tree_gui.cpp
@@ -166,6 +166,7 @@ static const NWidgetPart _nested_build_t
 	NWidget(NWID_HORIZONTAL),
 		NWidget(WWT_CLOSEBOX, COLOUR_DARK_GREEN),
 		NWidget(WWT_CAPTION, COLOUR_DARK_GREEN), SetDataTip(STR_PLANT_TREE_CAPTION, STR_TOOLTIP_WINDOW_TITLE_DRAG_THIS),
+		NWidget(WWT_STICKYBOX, COLOUR_DARK_GREEN),
 	EndContainer(),
 	NWidget(WWT_PANEL, COLOUR_DARK_GREEN),
 		NWidget(NWID_SPACER), SetMinimalSize(0, 2),