diff --git a/src/openrct2/ride/gentle/crooked_house.c b/src/openrct2/ride/gentle/crooked_house.c
index fb583ec62b..38c32bf559 100644
--- a/src/openrct2/ride/gentle/crooked_house.c
+++ b/src/openrct2/ride/gentle/crooked_house.c
@@ -51,7 +51,7 @@ static void paint_crooked_house_structure(uint8 direction, uint8 x_offset, uint8
     rct_ride_entry *ride_type = get_ride_entry(ride->subtype);
 
     if (ride->lifecycle_flags & RIDE_LIFECYCLE_ON_TRACK) {
-        if (ride->vehicles[0] != (uint16)-1) {
+        if (ride->vehicles[0] != SPRITE_INDEX_NULL) {
             rct_sprite *sprite = get_sprite(ride->vehicles[0]);
             gPaintInteractionType = VIEWPORT_INTERACTION_ITEM_SPRITE;
             g_currently_drawn_item = sprite;
diff --git a/src/openrct2/ride/ride.h b/src/openrct2/ride/ride.h
index 0997206d5c..50d8c799a1 100644
--- a/src/openrct2/ride/ride.h
+++ b/src/openrct2/ride/ride.h
@@ -23,6 +23,9 @@
 #include "vehicle.h"
 
 #define MAX_RIDE_TYPES_PER_RIDE_ENTRY   3
+// The max number of different types of vehicle.
+// Examples of vehicles here are the locomotive, tender and carriage of the Miniature Railway.
+#define MAX_VEHICLES_PER_RIDE_ENTRY     4
 #define RIDE_ENTRY_INDEX_NULL           255
 typedef fixed16_2dp ride_rating;
 
@@ -118,7 +121,7 @@ typedef struct rct_ride_entry {
     uint8 rear_vehicle;                                 // 0x017
     uint8 third_vehicle;                                // 0x018
     uint8 pad_019;                                      // 0x019
-    rct_ride_entry_vehicle vehicles[4];                 // 0x01A
+    rct_ride_entry_vehicle vehicles[MAX_VEHICLES_PER_RIDE_ENTRY];                 // 0x01A
     vehicle_colour_preset_list *vehicle_preset_list;    // 0x1AE
     sint8 excitement_multipler;                         // 0x1B2
     sint8 intensity_multipler;                          // 0x1B3
diff --git a/src/openrct2/ride/vehicle.c b/src/openrct2/ride/vehicle.c
index 733f37dcde..6c772014fa 100644
--- a/src/openrct2/ride/vehicle.c
+++ b/src/openrct2/ride/vehicle.c
@@ -761,7 +761,7 @@ sint32 sub_6BC2F3(rct_vehicle* vehicle)
     rct_vehicle* vehicle_temp = vehicle;
     do {
         result += vehicle_temp->friction;
-    } while (vehicle_temp->next_vehicle_on_train != (uint16)-1 && (vehicle_temp = GET_VEHICLE(vehicle_temp->next_vehicle_on_train)) != NULL);
+    } while (vehicle_temp->next_vehicle_on_train != SPRITE_INDEX_NULL && (vehicle_temp = GET_VEHICLE(vehicle_temp->next_vehicle_on_train)) != NULL);
     sint32 v4 = vehicle->velocity;
     if (v4 < 0) {
         v4 = -v4;