diff --git a/src/vehicle_gui.cpp b/src/vehicle_gui.cpp
--- a/src/vehicle_gui.cpp
+++ b/src/vehicle_gui.cpp
@@ -1805,7 +1805,7 @@ struct VehicleDetailsWindow : Window {
 				Dimension dim = { 0, 0 };
 				size->height = WD_FRAMERECT_TOP + 4 * FONT_HEIGHT_NORMAL + WD_FRAMERECT_BOTTOM;
 
-				for (uint i = 0; i < 4; i++) SetDParam(i, INT16_MAX);
+				for (uint i = 0; i < 4; i++) SetDParamMaxValue(i, INT16_MAX);
 				static const StringID info_strings[] = {
 					STR_VEHICLE_INFO_MAX_SPEED,
 					STR_VEHICLE_INFO_WEIGHT_POWER_MAX_SPEED,
@@ -1849,8 +1849,8 @@ struct VehicleDetailsWindow : Window {
 				break;
 
 			case WID_VD_SERVICING_INTERVAL:
-				SetDParam(0, 9999); // Roughly the maximum interval
-				SetDParam(1, MAX_YEAR * DAYS_IN_YEAR); // Roughly the maximum year
+				SetDParamMaxValue(0, MAX_SERVINT_DAYS); // Roughly the maximum interval
+				SetDParamMaxValue(1, MAX_YEAR * DAYS_IN_YEAR); // Roughly the maximum year
 				size->width = max(GetStringBoundingBox(STR_VEHICLE_DETAILS_SERVICING_INTERVAL_PERCENT).width, GetStringBoundingBox(STR_VEHICLE_DETAILS_SERVICING_INTERVAL_DAYS).width) + WD_FRAMERECT_LEFT + WD_FRAMERECT_RIGHT;
 				size->height = WD_FRAMERECT_TOP + FONT_HEIGHT_NORMAL + WD_FRAMERECT_BOTTOM;
 				break;