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
@@ -666,9 +666,9 @@ bool LinkGraphLegendWindow::OnTooltip([[
 void LinkGraphLegendWindow::UpdateOverlayCompanies()
 {
 	uint32_t mask = 0;
-	for (uint c = 0; c < MAX_COMPANIES; c++) {
-		if (this->IsWidgetDisabled(c + WID_LGL_COMPANY_FIRST)) continue;
-		if (!this->IsWidgetLowered(c + WID_LGL_COMPANY_FIRST)) continue;
+	for (CompanyID c = COMPANY_FIRST; c < MAX_COMPANIES; c++) {
+		if (this->IsWidgetDisabled(WID_LGL_COMPANY_FIRST + c)) continue;
+		if (!this->IsWidgetLowered(WID_LGL_COMPANY_FIRST + c)) continue;
 		SetBit(mask, c);
 	}
 	this->overlay->SetCompanyMask(mask);
@@ -680,8 +680,8 @@ void LinkGraphLegendWindow::UpdateOverla
 void LinkGraphLegendWindow::UpdateOverlayCargoes()
 {
 	CargoTypes mask = 0;
-	for (uint c = 0; c < num_cargo; c++) {
-		if (!this->IsWidgetLowered(c + WID_LGL_CARGO_FIRST)) continue;
+	for (CompanyID c = COMPANY_FIRST; c < MAX_COMPANIES; c++) {
+		if (!this->IsWidgetLowered(WID_LGL_CARGO_FIRST + c)) continue;
 		SetBit(mask, _sorted_cargo_specs[c]->Index());
 	}
 	this->overlay->SetCargoMask(mask);
@@ -696,8 +696,8 @@ void LinkGraphLegendWindow::OnClick([[ma
 			this->UpdateOverlayCompanies();
 		}
 	} else if (widget == WID_LGL_COMPANIES_ALL || widget == WID_LGL_COMPANIES_NONE) {
-		for (uint c = 0; c < MAX_COMPANIES; c++) {
-			if (this->IsWidgetDisabled(c + WID_LGL_COMPANY_FIRST)) continue;
+		for (CompanyID c = COMPANY_FIRST; c < MAX_COMPANIES; c++) {
+			if (this->IsWidgetDisabled(WID_LGL_COMPANY_FIRST + c)) continue;
 			this->SetWidgetLoweredState(WID_LGL_COMPANY_FIRST + c, widget == WID_LGL_COMPANIES_ALL);
 		}
 		this->UpdateOverlayCompanies();
@@ -728,6 +728,6 @@ void LinkGraphLegendWindow::OnInvalidate
 
 	/* Disable the companies who are not active */
 	for (CompanyID i = COMPANY_FIRST; i < MAX_COMPANIES; i++) {
-		this->SetWidgetDisabledState(i + WID_LGL_COMPANY_FIRST, !Company::IsValidID(i));
+		this->SetWidgetDisabledState(WID_LGL_COMPANY_FIRST + i, !Company::IsValidID(i));
 	}
 }