diff --git a/src/linkgraph/linkgraph_gui.cpp b/src/linkgraph/linkgraph_gui.cpp
--- a/src/linkgraph/linkgraph_gui.cpp
+++ b/src/linkgraph/linkgraph_gui.cpp
@@ -506,7 +506,7 @@ std::unique_ptr<NWidgetBase> MakeCargoes
 }
 
 
-static const NWidgetPart _nested_linkgraph_legend_widgets[] = {
+static constexpr NWidgetPart _nested_linkgraph_legend_widgets[] = {
 	NWidget(NWID_HORIZONTAL),
 		NWidget(WWT_CLOSEBOX, COLOUR_DARK_GREEN),
 		NWidget(WWT_CAPTION, COLOUR_DARK_GREEN, WID_LGL_CAPTION), SetDataTip(STR_LINKGRAPH_LEGEND_CAPTION, STR_TOOLTIP_WINDOW_TITLE_DRAG_THIS),