diff --git a/src/order_gui.cpp b/src/order_gui.cpp
index e916d3d72f..fc889d3fe0 100644
--- a/src/order_gui.cpp
+++ b/src/order_gui.cpp
@@ -1166,7 +1166,11 @@ public:
 			case WID_O_DEPOT_ACTION: {
 				VehicleOrderID sel = this->OrderGetSel();
 				const Order *order = this->vehicle->GetOrder(sel);
-				if (order == nullptr || !order->IsType(OT_GOTO_DEPOT)) break;
+				if (order == nullptr || !order->IsType(OT_GOTO_DEPOT)) {
+					/* We can't leave this param unset or the undefined behavior can cause a crash. */
+					SetDParam(0, STR_EMPTY);
+					break;
+				};
 
 				/* Select the current action selected in the dropdown. The flags don't match the dropdown so we can't just use an index. */
 				if (order->GetDepotOrderType() & ODTFB_SERVICE) {