diff --git a/src/openrct2/editor.c b/src/openrct2/editor.c
index 07c8c95d20..61b3d6d2d5 100644
--- a/src/openrct2/editor.c
+++ b/src/openrct2/editor.c
@@ -14,36 +14,36 @@
  *****************************************************************************/
 #pragma endregion
 
-#include "rct2/addresses.h"
 #include "audio/audio.h"
 #include "drawing/drawing.h"
 #include "editor.h"
 #include "game.h"
-#include "interface/window.h"
 #include "interface/viewport.h"
+#include "interface/window.h"
 #include "localisation/date.h"
 #include "localisation/localisation.h"
 #include "management/finance.h"
 #include "management/news_item.h"
+#include "network/network.h"
 #include "object.h"
 #include "object/ObjectManager.h"
 #include "peep/staff.h"
 #include "platform/platform.h"
 #include "rct1.h"
+#include "rct2/addresses.h"
 #include "ride/ride.h"
 #include "ParkImporter.h"
 #include "scenario/scenario.h"
 #include "util/sawyercoding.h"
 #include "util/util.h"
-#include "world/banner.h"
 #include "world/Climate.h"
-#include "world/footpath.h"
+#include "world/banner.h"
 #include "world/entrance.h"
+#include "world/footpath.h"
 #include "world/map.h"
 #include "world/park.h"
 #include "world/scenery.h"
 #include "world/sprite.h"
-#include "network/network.h"
 
 uint8 _editorSelectedRides[128];
 uint8 _editorSelectedSmallScenery[252];
@@ -411,7 +411,7 @@ static void editor_finalise_main_view()
     rct_window *w = window_get_main();
     rct_viewport *viewport = w->viewport;
 
-    w->viewport_target_sprite = -1;
+    w->viewport_target_sprite = SPRITE_INDEX_NULL;
     w->saved_view_x = gSavedViewX;
     w->saved_view_y = gSavedViewY;
     gCurrentRotation = gSavedViewRotation;
diff --git a/src/openrct2/game.c b/src/openrct2/game.c
index 9f7ecab429..e199c66c86 100644
--- a/src/openrct2/game.c
+++ b/src/openrct2/game.c
@@ -1154,7 +1154,7 @@ void game_load_init()
     game_create_windows();
     mainWindow = window_get_main();
 
-    mainWindow->viewport_target_sprite = -1;
+    mainWindow->viewport_target_sprite = SPRITE_INDEX_NULL;
     mainWindow->saved_view_x = gSavedViewX;
     mainWindow->saved_view_y = gSavedViewY;
     uint8 zoomDifference = gSavedViewZoom - mainWindow->viewport->zoom;
diff --git a/src/openrct2/interface/viewport.c b/src/openrct2/interface/viewport.c
index 4e9ec839e3..0c026f4ce7 100644
--- a/src/openrct2/interface/viewport.c
+++ b/src/openrct2/interface/viewport.c
@@ -26,7 +26,6 @@
 #include "../rct2.h"
 #include "../ride/ride_data.h"
 #include "../ride/track_data.h"
-#include "../sprites.h"
 #include "../world/banner.h"
 #include "../world/Climate.h"
 #include "../world/entrance.h"
@@ -193,7 +192,7 @@ void viewport_create(rct_window *w, sint32 x, sint32 y, sint32 width, sint32 hei
         centre_z = centre_sprite->unknown.z;
     }
     else{
-        w->viewport_target_sprite = SPR_NONE;
+        w->viewport_target_sprite = SPRITE_INDEX_NULL;
     }
 
     sint32 view_x, view_y;
@@ -520,7 +519,7 @@ void viewport_update_position(rct_window *window)
     rct_viewport* viewport = window->viewport;
     if (!viewport)return;
 
-    if (window->viewport_target_sprite != -1) {
+    if (window->viewport_target_sprite != SPRITE_INDEX_NULL) {
         viewport_update_sprite_follow(window);
         return;
     }
@@ -605,7 +604,7 @@ void viewport_update_position(rct_window *window)
 
 void viewport_update_sprite_follow(rct_window *window)
 {
-    if (window->viewport_target_sprite != -1 && window->viewport){
+    if (window->viewport_target_sprite != SPRITE_INDEX_NULL && window->viewport) {
         rct_sprite* sprite = get_sprite(window->viewport_target_sprite);
 
         sint32 height = (map_element_height(0xFFFF & sprite->unknown.x, 0xFFFF & sprite->unknown.y) & 0xFFFF) - 16;
diff --git a/src/openrct2/interface/window.c b/src/openrct2/interface/window.c
index 62ce96f443..564ad41bd3 100644
--- a/src/openrct2/interface/window.c
+++ b/src/openrct2/interface/window.c
@@ -15,14 +15,15 @@
 #pragma endregion
 
 #include "../audio/audio.h"
+#include "../config/Config.h"
 #include "../Context.h"
 #include "../core/Guard.hpp"
 #include "../drawing/drawing.h"
 #include "../editor.h"
 #include "../game.h"
 #include "../input.h"
-#include "../interface/themes.h"
 #include "../interface/Cursors.h"
+#include "../interface/themes.h"
 #include "../localisation/localisation.h"
 #include "../localisation/string_ids.h"
 #include "../platform/platform.h"
@@ -31,7 +32,6 @@
 #include "viewport.h"
 #include "widget.h"
 #include "window.h"
-#include "../config/Config.h"
 
 #define RCT2_FIRST_WINDOW       (g_window_list)
 #define RCT2_LAST_WINDOW        (gWindowNextSlot - 1)
@@ -1402,7 +1402,7 @@ void window_scroll_to_location(rct_window *w, sint32 x, sint32 y, sint32 z)
             }
         }
         // rct2: 0x006E7C76
-        if (w->viewport_target_sprite == -1) {
+        if (w->viewport_target_sprite == SPRITE_INDEX_NULL) {
             if (!(w->flags & WF_NO_SCROLLING)) {
                 w->saved_view_x = map_coordinate.x - (sint16)(w->viewport->view_width * window_scroll_locations[i][0]);
                 w->saved_view_y = map_coordinate.y - (sint16)(w->viewport->view_height * window_scroll_locations[i][1]);
diff --git a/src/openrct2/interface/window.h b/src/openrct2/interface/window.h
index f38e7bcfe3..f42ddcc793 100644
--- a/src/openrct2/interface/window.h
+++ b/src/openrct2/interface/window.h
@@ -300,7 +300,7 @@ typedef struct rct_window {
     uint8 var_498[0x14];
     sint16 selected_tab;            // 0x4AC
     sint16 var_4AE;
-    sint16 viewport_target_sprite;  // 0x4B0 viewport target sprite?
+    uint16 viewport_target_sprite;  // 0x4B0 viewport target sprite
     sint16 saved_view_x;            // 0x4B2
     sint16 saved_view_y;            // 0x4B4
     rct_windowclass classification; // 0x4B6
diff --git a/src/openrct2/scenario/scenario.c b/src/openrct2/scenario/scenario.c
index 2e1a7d6277..c7bfb3848a 100644
--- a/src/openrct2/scenario/scenario.c
+++ b/src/openrct2/scenario/scenario.c
@@ -43,9 +43,9 @@
 #include "../world/scenery.h"
 #include "../world/sprite.h"
 #include "../world/water.h"
-#include "scenario.h"
 #include "ScenarioRepository.h"
 #include "ScenarioSources.h"
+#include "scenario.h"
 
 const rct_string_id ScenarioCategoryStringIds[SCENARIO_CATEGORY_COUNT] = {
     STR_BEGINNER_PARKS,
@@ -151,7 +151,7 @@ void scenario_begin()
     game_create_windows();
     mainWindow = window_get_main();
 
-    mainWindow->viewport_target_sprite = -1;
+    mainWindow->viewport_target_sprite = SPRITE_INDEX_NULL;
     mainWindow->saved_view_x = gSavedViewX;
     mainWindow->saved_view_y = gSavedViewY;
 
diff --git a/src/openrct2/title/TitleSequencePlayer.cpp b/src/openrct2/title/TitleSequencePlayer.cpp
index 728ca3d6c2..378718ff25 100644
--- a/src/openrct2/title/TitleSequencePlayer.cpp
+++ b/src/openrct2/title/TitleSequencePlayer.cpp
@@ -404,7 +404,7 @@ private:
     void PrepareParkForPlayback()
     {
         rct_window * w = window_get_main();
-        w->viewport_target_sprite = -1;
+        w->viewport_target_sprite = SPRITE_INDEX_NULL;
         w->saved_view_x = gSavedViewX;
         w->saved_view_y = gSavedViewY;
 
diff --git a/src/openrct2/windows/guest.c b/src/openrct2/windows/guest.c
index 65ad7f2fb4..ac1c8097c1 100644
--- a/src/openrct2/windows/guest.c
+++ b/src/openrct2/windows/guest.c
@@ -719,7 +719,7 @@ void window_guest_viewport_init(rct_window* w){
     rct_peep* peep = GET_PEEP(w->number);
 
     if (peep->state == PEEP_STATE_PICKED){
-        focus.sprite.sprite_id = -1;
+        focus.sprite.sprite_id = SPRITE_INDEX_NULL;
     }
     else{
         uint8 final_check = 1;
diff --git a/src/openrct2/windows/ride.c b/src/openrct2/windows/ride.c
index a4862a3765..47de44c416 100644
--- a/src/openrct2/windows/ride.c
+++ b/src/openrct2/windows/ride.c
@@ -1777,7 +1777,7 @@ static void window_ride_init_viewport(rct_window *w)
     focus.coordinate.x = 0;
     focus.coordinate.y = 0;
     focus.coordinate.z = 0;
-    focus.sprite.sprite_id = -1;
+    focus.sprite.sprite_id = SPRITE_INDEX_NULL;
     focus.coordinate.zoom = 0;
     focus.coordinate.rotation = get_current_rotation();
     focus.coordinate.width = 0;
diff --git a/src/openrct2/windows/staff.c b/src/openrct2/windows/staff.c
index ec57e93fe5..27072d7dd7 100644
--- a/src/openrct2/windows/staff.c
+++ b/src/openrct2/windows/staff.c
@@ -1220,7 +1220,7 @@ void window_staff_viewport_init(rct_window* w){
     rct_peep* peep = GET_PEEP(w->number);
 
     if (peep->state == PEEP_STATE_PICKED){
-        focus.sprite_id = -1;
+        focus.sprite_id = SPRITE_INDEX_NULL;
     }
     else{
         focus.type |= VIEWPORT_FOCUS_TYPE_SPRITE | VIEWPORT_FOCUS_TYPE_COORDINATE;
diff --git a/src/openrct2/world/sprite.c b/src/openrct2/world/sprite.c
index cdc00cb15c..e313a71106 100644
--- a/src/openrct2/world/sprite.c
+++ b/src/openrct2/world/sprite.c
@@ -166,7 +166,7 @@ void reset_sprite_list()
  */
 void reset_sprite_spatial_index()
 {
-    memset(gSpriteSpatialIndex, -1, sizeof(gSpriteSpatialIndex));
+    memset(gSpriteSpatialIndex, SPRITE_INDEX_NULL, sizeof(gSpriteSpatialIndex));
     for (size_t i = 0; i < MAX_SPRITES; i++) {
         rct_sprite *spr = get_sprite(i);
         if (spr->unknown.sprite_identifier != SPRITE_IDENTIFIER_NULL) {