diff --git a/src/build_vehicle_gui.cpp b/src/build_vehicle_gui.cpp
index b1d2e7e671..f00aacce5e 100644
--- a/src/build_vehicle_gui.cpp
+++ b/src/build_vehicle_gui.cpp
@@ -710,7 +710,7 @@ static int DrawRailWagonPurchaseInfo(int left, int right, int y, EngineID engine
 	/* Wagon weight - (including cargo) */
 	uint weight = e->GetDisplayWeight();
 	SetDParam(0, weight);
-	uint cargo_weight = (e->CanCarryCargo() ? CargoSpec::Get(te.cargo)->weight * te.capacity / 16 : 0);
+	uint cargo_weight = ((e->CanCarryCargo() && te.cargo < NUM_CARGO) ? CargoSpec::Get(te.cargo)->weight * te.capacity / 16 : 0);
 	SetDParam(1, cargo_weight + weight);
 	DrawString(left, right, y, STR_PURCHASE_INFO_WEIGHT_CWEIGHT);
 	y += FONT_HEIGHT_NORMAL;
@@ -804,7 +804,7 @@ static int DrawRoadVehPurchaseInfo(int left, int right, int y, EngineID engine_n
 		/* Road vehicle weight - (including cargo) */
 		int16 weight = e->GetDisplayWeight();
 		SetDParam(0, weight);
-		uint cargo_weight = (e->CanCarryCargo() ? CargoSpec::Get(te.cargo)->weight * te.capacity / 16 : 0);
+		uint cargo_weight = ((e->CanCarryCargo() && te.cargo < NUM_CARGO) ? CargoSpec::Get(te.cargo)->weight * te.capacity / 16 : 0);
 		SetDParam(1, cargo_weight + weight);
 		DrawString(left, right, y, STR_PURCHASE_INFO_WEIGHT_CWEIGHT);
 		y += FONT_HEIGHT_NORMAL;