diff --git a/src/acs/environment.cpp b/src/acs/environment.cpp
index 317fc6018..41967d293 100644
--- a/src/acs/environment.cpp
+++ b/src/acs/environment.cpp
@@ -275,7 +275,7 @@ void Environment::loadModule(ACSVM::Module *module)
 
 	if (name->i) // this module is from a map!
 	{
-		INT32 mapnum = G_MapNumber(name->s->str);
+		UINT16 mapnum = G_MapNumber(name->s->str);
 		if (mapnum < NEXTMAP_INVALID)
 			lumpnum = mapheaderinfo[mapnum]->lumpnum;
 	}
diff --git a/src/d_netcmd.c b/src/d_netcmd.c
index 368c83aff..fee2f5a4f 100644
--- a/src/d_netcmd.c
+++ b/src/d_netcmd.c
@@ -3340,18 +3340,13 @@ INT32 mapchangepending = 0;
   * \sa D_GameTypeChanged, Command_Map_f
   * \author Graue <graue@oceanbase.org>
   */
-void D_MapChange(INT32 mapnum, INT32 newgametype, boolean pencoremode, boolean presetplayers, INT32 delay, boolean skipprecutscene, boolean pforcespecialstage)
+void D_MapChange(UINT16 mapnum, INT32 newgametype, boolean pencoremode, boolean presetplayers, INT32 delay, boolean skipprecutscene, boolean pforcespecialstage)
 {
 	static char buf[1+1+1+1+1+2+4];
 	static char *buf_p = buf;
 	// The supplied data are assumed to be good.
 	I_Assert(delay >= 0 && delay <= 2);
 
-	if (mapnum != -1)
-	{
-		CV_SetValue(&cv_nextmap, mapnum);
-	}
-
 	CONS_Debug(DBG_GAMELOGIC, "Map change: mapnum=%d gametype=%d pencoremode=%d presetplayers=%d delay=%d skipprecutscene=%d pforcespecialstage = %d\n",
 			   mapnum, newgametype, pencoremode, presetplayers, delay, skipprecutscene, pforcespecialstage);
 
@@ -3384,7 +3379,7 @@ void D_MapChange(INT32 mapnum, INT32 newgametype, boolean pencoremode, boolean p
 		// new gametype value
 		WRITEUINT16(buf_p, newgametype);
 
-		WRITEINT16(buf_p, mapnum);
+		WRITEUINT16(buf_p, mapnum);
 	}
 
 	if (delay == 1)
@@ -3928,7 +3923,7 @@ static void Got_Mapcmd(UINT8 **cp, INT32 playernum)
 	UINT8 skipprecutscene, pforcespecialstage;
 	boolean pencoremode, hasroundqueuedata;
 	UINT16 lastgametype;
-	INT16 mapnumber;
+	UINT16 mapnumber;
 
 	forceresetplayers = deferencoremode = false;
 
@@ -4007,7 +4002,7 @@ static void Got_Mapcmd(UINT8 **cp, INT32 playernum)
 	if (!(gametypes[gametype]->rules & GTR_ENCORE) && !bossinfo.boss)
 		pencoremode = false;
 
-	mapnumber = READINT16(*cp);
+	mapnumber = READUINT16(*cp);
 
 	// Handle some Grand Prix state.
 	if (grandprixinfo.gp)
diff --git a/src/d_netcmd.h b/src/d_netcmd.h
index 2924fc2cf..9ebbec6c9 100644
--- a/src/d_netcmd.h
+++ b/src/d_netcmd.h
@@ -404,7 +404,7 @@ void D_SendPlayerConfig(UINT8 n);
 void Command_ExitGame_f(void);
 void Command_Retry_f(void);
 void D_GameTypeChanged(INT32 lastgametype); // not a real _OnChange function anymore
-void D_MapChange(INT32 pmapnum, INT32 pgametype, boolean pencoremode, boolean presetplayers, INT32 pdelay, boolean pskipprecutscene, boolean pforcespecialstage);
+void D_MapChange(UINT16 pmapnum, INT32 pgametype, boolean pencoremode, boolean presetplayers, INT32 pdelay, boolean pskipprecutscene, boolean pforcespecialstage);
 void D_SetupVote(void);
 void D_ModifyClientVote(UINT8 player, SINT8 voted);
 void D_PickVote(void);
diff --git a/src/deh_soc.c b/src/deh_soc.c
index 4eaa51263..247bb461a 100644
--- a/src/deh_soc.c
+++ b/src/deh_soc.c
@@ -790,7 +790,7 @@ void readgametype(MYFILE *f, char *gtname)
 	CONS_Printf("Added gametype %s\n", gtname);
 }
 
-static mapheader_lighting_t *usemaplighting(INT32 mapnum, const char *word)
+static mapheader_lighting_t *usemaplighting(UINT16 mapnum, const char *word)
 {
 	if (fastncmp(word, "ENCORE", 6))
 	{
@@ -853,7 +853,7 @@ if (fastcmp(word, name)) \
 		OUTOFRANGE_CONSTANT(name, word2, minname, maxname); \
 }
 
-static void processvector(const char* name, INT32 mapnum, char *word2, f_vector3_t *vec, float min, float max)
+static void processvector(const char* name, UINT16 mapnum, char *word2, f_vector3_t *vec, float min, float max)
 {
 	char *tmp = strtok(word2,",");
 	float vector[3];
@@ -878,7 +878,7 @@ static void processvector(const char* name, INT32 mapnum, char *word2, f_vector3
 }
 
 // Handle parsing globalefx info
-static void globalmapefxparameters(INT32 mapnum, INT32 i, char *word, char *word2)
+static void globalmapefxparameters(UINT16 mapnum, INT32 i, char *word, char *word2)
 {
 	// Take off GLOBALEFX_
 	word += 10;
@@ -1068,7 +1068,7 @@ void readlevelheader(MYFILE *f, char * name)
 		name = va("MAP%s", name);
 	}
 
-	INT32 num = G_MapNumber(name);
+	UINT16 num = G_MapNumber(name);
 
 	if (num >= nummapheaders)
 	{
@@ -3166,7 +3166,7 @@ void readunlockable(MYFILE *f, INT32 num)
 				{
 					Z_Free(unlockables[num].stringVar);
 					unlockables[num].stringVar = Z_StrDup(word2);
-					unlockables[num].variable = (INT16)G_MapNumber(word2);
+					unlockables[num].variable = (UINT16)G_MapNumber(word2);
 				}
 				else
 					deh_warning("Unlockable %d: unknown word '%s'", num+1, word);
diff --git a/src/doomstat.h b/src/doomstat.h
index 6413d612a..e230d0e26 100644
--- a/src/doomstat.h
+++ b/src/doomstat.h
@@ -36,7 +36,7 @@ extern "C" {
 // =============================
 
 // Selected by user.
-extern INT16 gamemap;
+extern UINT16 gamemap;
 extern char mapmusname[7];
 extern UINT16 mapmusflags;
 extern UINT32 mapmusposition;
@@ -347,7 +347,7 @@ struct cupheader_t
 
 	char icon[9];							///< Name of the icon patch
 	char *levellist[CUPCACHE_MAX];			///< List of levels that belong to this cup
-	INT16 cachedlevels[CUPCACHE_MAX];		///< IDs in levellist, bonusgame, and specialstage
+	UINT16 cachedlevels[CUPCACHE_MAX];		///< IDs in levellist, bonusgame, and specialstage
 	UINT8 numlevels;						///< Number of levels defined in levellist
 	UINT8 numbonus;							///< Number of bonus stages defined
 	UINT8 emeraldnum;						///< ID of Emerald to use for special stage (1-7 for Chaos Emeralds, 8-14 for Super Emeralds, 0 for no emerald)
diff --git a/src/g_game.c b/src/g_game.c
index 142db29d9..8b01b5597 100644
--- a/src/g_game.c
+++ b/src/g_game.c
@@ -102,7 +102,7 @@ UINT32 mapmusposition; // Position to jump to
 UINT32 mapmusresume;
 UINT8 mapmusrng; // Random selection result
 
-INT16 gamemap = 1;
+UINT16 gamemap = 1;
 UINT32 maptol;
 
 preciptype_t globalweather = PRECIP_NONE;
@@ -352,10 +352,10 @@ typedef struct joystickvector2_s
 	INT32 yaxis;
 } joystickvector2_t;
 
-INT16 prevmap, nextmap;
+UINT16 prevmap, nextmap;
 
-INT16 kartmap2native[NEXTMAP_SPECIAL] = {0}, nativemap2kart[NEXTMAP_SPECIAL] = {0};
-INT16 nextexnum = NUMMAPS;
+UINT16 kartmap2native[NEXTMAP_SPECIAL] = {0}, nativemap2kart[NEXTMAP_SPECIAL] = {0};
+UINT16 nextexnum = NUMMAPS;
 
 // don't mind me putting these here, I was lazy to figure out where else I could put those without blowing up the compiler.
 
@@ -777,7 +777,7 @@ void G_ClearRecords(void)
 
 // For easy retrieval of records
 // TODO: should this work for unloaded maps?
-tic_t G_GetBestTime(INT16 map)
+tic_t G_GetBestTime(UINT16 map)
 {
 	const char *mapname = G_BuildMapName(map + 1);
 	tic_t besttime = UINT32_MAX;
@@ -1006,7 +1006,7 @@ void G_SetGameModified(boolean silent, boolean major)
   * \return Pointer to a static buffer containing the desired map name.
   * \sa G_MapNumber
   */
-const char *G_BuildMapName(INT32 map)
+const char *G_BuildMapName(UINT16 map)
 {
 	if (map > 0 && map <= nummapheaders && mapheaderinfo[map - 1] != NULL)
 	{
@@ -1024,13 +1024,13 @@ const char *G_BuildMapName(INT32 map)
   * \return Map number.
   * \sa G_BuildMapName, nextmapspecial_t
   */
-INT32 G_MapNumber(const char * name)
+UINT16 G_MapNumber(const char * name)
 {
 #ifdef NEXTMAPINSOC
 	if (strncasecmp("NEXTMAP_", name, 8) != 0)
 #endif
 	{
-		INT32 map;
+		UINT16 map;
 		UINT32 hash = FNV1a_QuickCaseHash(name, MAXMAPLUMPNAME);
 
 		for (map = 0; map < nummapheaders; ++map)
@@ -1067,9 +1067,9 @@ INT32 G_MapNumber(const char * name)
   * \return Map number.
   * \sa G_BuildMapName, nextmapspecial_t
   */
-INT32 G_LevelTitleToMapNum(const char * leveltitle)
+UINT16 G_LevelTitleToMapNum(const char * leveltitle)
 {
-	INT32 map;
+	UINT16  map;
 	char levelname[48];
 
 	for (map = 0; map < nummapheaders; ++map)
@@ -1099,11 +1099,11 @@ INT32 G_LevelTitleToMapNum(const char * leveltitle)
 		}
 
 	}
-	return INT32_MIN;
+	return NEXTMAP_INVALID;
 }
 
 // convert kart map number to native map number
-INT16 G_KartMapToNative(INT16 mapnum)
+UINT16 G_KartMapToNative(UINT16 mapnum)
 {
 	if (mapnum > 0 && mapnum < NEXTMAP_SPECIAL)
 		return kartmap2native[mapnum-1];
@@ -1111,7 +1111,7 @@ INT16 G_KartMapToNative(INT16 mapnum)
 }
 
 // convert native map number to kart
-INT16 G_NativeMapToKart(INT16 mapnum)
+UINT16 G_NativeMapToKart(UINT16 mapnum)
 {
 	if (mapnum > 0 && mapnum < NEXTMAP_SPECIAL)
 		return nativemap2kart[mapnum-1]+1;
@@ -4374,7 +4374,7 @@ void G_AddTOL(UINT32 newtol, const char *tolname)
 // Returns TRUE if
 // the given map is a special stage.
 //
-boolean G_IsSpecialStage(INT32 mapnum)
+boolean G_IsSpecialStage(UINT16 mapnum)
 {
 	mapnum--; // gamemap-based to 0 indexed
 
@@ -4558,7 +4558,7 @@ UINT32 G_TOLFlag(INT32 pgametype)
 
 INT16 G_GetFirstMapOfGametype(UINT8 pgametype)
 {
-	INT16 mapnum = NEXTMAP_INVALID;
+	UINT16 mapnum = NEXTMAP_INVALID;
 
 	/* G: not sure what to do with this
 	if ((gametypes[pgametype]->rules & GTR_CAMPAIGN) && kartcupheaders)
@@ -4772,7 +4772,7 @@ tryagain:
 	return ix;
 }
 
-void G_AddMapToBuffer(INT16 map)
+void G_AddMapToBuffer(UINT16 map)
 {
 	INT16 bufx;
 	INT16 refreshnum = (TOLMaps(gametype))-3;
@@ -4848,7 +4848,7 @@ static void G_UpdateVisited(void)
 		//CONS_Printf(M_GetText("\x82" "Earned %hu emblem%s for level completion.\n"), (UINT16)earnedEmblems, earnedEmblems > 1 ? "s" : "");
 }
 
-static boolean CanSaveLevel(INT32 mapnum)
+static boolean CanSaveLevel(UINT16 mapnum)
 {
 	// SRB2Kart: No save files yet
 	(void)mapnum;
@@ -5001,13 +5001,13 @@ void G_GetNextMap(void)
 	deferencoremode = (cv_kartencore.value == 1);
 	forceresetplayers = forcespecialstage = false;
 
-	INT16 newmap, curmap = gamestate == GS_LEVEL ? gamemap-1 : prevmap;
+	UINT16 newmap, curmap = gamestate == GS_LEVEL ? gamemap-1 : prevmap;
 
 	// go to next level
 	// nextmap is 0-based, unlike gamemap
 	if (nextmapoverride != 0)
 	{
-		newmap = (INT16)(nextmapoverride-1);
+		newmap = (UINT16)(nextmapoverride-1);
 		setalready = true;
 	}
 	else if (roundqueue.size > 0)
@@ -5559,7 +5559,7 @@ static boolean LoadLegacyRecords(savebuffer_t *save)
 	for (UINT32 i = 0; i < numgamedatamapheaders; i++)
 	{
 		char mapname[MAXMAPLUMPNAME];
-		//INT16 mapnum;
+		//UINT16 mapnum;
 		tic_t rectime;
 		tic_t reclap;
 
@@ -5933,7 +5933,7 @@ void G_SaveGameData(void)
 // G_InitFromSavegame
 // Can be called by the startup code or the menu task.
 //
-void G_LoadGame(UINT32 slot, INT16 mapoverride)
+void G_LoadGame(UINT32 slot, UINT16 mapoverride)
 {
 	char vcheck[VERSIONSIZE];
 	char savename[255];
@@ -6026,7 +6026,7 @@ void G_LoadGame(UINT32 slot, INT16 mapoverride)
 // G_SaveGame
 // Saves your game.
 //
-void G_SaveGame(UINT32 slot, INT16 mapnum)
+void G_SaveGame(UINT32 slot, UINT16 mapnum)
 {
 	boolean saved;
 	char savename[256] = "";
@@ -6188,7 +6188,7 @@ cleanup:
 // Can be called by the startup code or the menu task,
 // consoleplayer, displayplayers[], playeringame[] should be set.
 //
-void G_DeferedInitNew(boolean pencoremode, INT32 map, INT32 pickedchar, UINT8 ssplayers, boolean FLS)
+void G_DeferedInitNew(boolean pencoremode, UINT16 map, INT32 pickedchar, UINT8 ssplayers, boolean FLS)
 {
 	UINT16 color = SKINCOLOR_NONE;
 	INT32 dogametype;
@@ -6235,7 +6235,7 @@ void G_DeferedInitNew(boolean pencoremode, INT32 map, INT32 pickedchar, UINT8 ss
 // This is the map command interpretation something like Command_Map_f
 //
 // called at: map cmd execution, doloadgame, doplaydemo
-void G_InitNew(UINT8 pencoremode, INT32 map, boolean resetplayer, boolean skipprecutscene)
+void G_InitNew(UINT8 pencoremode, UINT16 map, boolean resetplayer, boolean skipprecutscene)
 {
 	const char * mapname = G_BuildMapName(map);
 
@@ -6336,7 +6336,7 @@ void G_InitNew(UINT8 pencoremode, INT32 map, boolean resetplayer, boolean skippr
 }
 
 
-char *G_BuildMapTitle(INT32 mapnum)
+char *G_BuildMapTitle(UINT16 mapnum)
 {
 	char *title = NULL;
 
@@ -6409,7 +6409,7 @@ static void measurekeywords(mapsearchfreq_t *fr,
 }
 
 static void writesimplefreq(mapsearchfreq_t *fr, INT32 *frc,
-		INT32 mapnum, UINT8 pos, UINT8 siz)
+		UINT16 mapnum, UINT8 pos, UINT8 siz)
 {
 	fr[(*frc)].mapnum = mapnum;
 	fr[(*frc)].matchd = ZZ_Alloc(sizeof (struct searchdim));
@@ -6420,12 +6420,12 @@ static void writesimplefreq(mapsearchfreq_t *fr, INT32 *frc,
 	(*frc)++;
 }
 
-INT32 G_FindMap(const char *mapname, char **foundmapnamep,
+UINT16 G_FindMap(const char *mapname, char **foundmapnamep,
 		mapsearchfreq_t **freqp, INT32 *freqcp)
 {
-	INT32 newmapnum = 0;
-	INT32 mapnum;
-	INT32 apromapnum = 0;
+	UINT16 newmapnum = 0;
+	UINT16 mapnum;
+	UINT16 apromapnum = 0;
 
 	size_t      mapnamelen;
 	char   *realmapname = NULL;
@@ -6558,7 +6558,7 @@ void G_FreeMapSearch(mapsearchfreq_t *freq, INT32 freqc)
 	Z_Free(freq);
 }
 
-INT32 G_FindMapByNameOrCode(const char *mapname, char **realmapnamep)
+UINT16 G_FindMapByNameOrCode(const char *mapname, char **realmapnamep)
 {
 	INT32 newmapnum;
 
diff --git a/src/g_game.h b/src/g_game.h
index 003f89fbf..0635ccfea 100644
--- a/src/g_game.h
+++ b/src/g_game.h
@@ -38,18 +38,18 @@ extern boolean playeringame[MAXPLAYERS];
 extern tic_t levelstarttic;
 
 // for modding?
-extern INT16 prevmap, nextmap;
+extern UINT16 prevmap, nextmap;
 
 // see also G_MapNumber
 typedef enum
 {
-	NEXTMAP_RESERVED = INT16_MAX, // so nextmap+1 doesn't roll over -- remove when gamemap is made 0-indexed
-	NEXTMAP_TITLE = INT16_MAX-1,
-	NEXTMAP_EVALUATION = INT16_MAX-2,
-	NEXTMAP_CREDITS = INT16_MAX-3,
-	NEXTMAP_CEREMONY = INT16_MAX-4,
-	NEXTMAP_VOTING = INT16_MAX-5,
-	NEXTMAP_INVALID = INT16_MAX-6, // Always last
+	NEXTMAP_RESERVED = UINT16_MAX, // so nextmap+1 doesn't roll over -- remove when gamemap is made 0-indexed
+	NEXTMAP_TITLE = UINT16_MAX-1,
+	NEXTMAP_EVALUATION = UINT16_MAX-2,
+	NEXTMAP_CREDITS = UINT16_MAX-3,
+	NEXTMAP_CEREMONY = UINT16_MAX-4,
+	NEXTMAP_VOTING = UINT16_MAX-5,
+	NEXTMAP_INVALID = UINT16_MAX-6, // Always last
 	NEXTMAP_SPECIAL = NEXTMAP_INVALID
 } nextmapspecial_t;
 
@@ -77,8 +77,8 @@ void G_MapSlipIntoRoundQueue(UINT8 position, UINT16 map, UINT8 setgametype, bool
 void G_MapIntoRoundQueue(UINT16 map, UINT8 setgametype, boolean setencore, boolean rankrestricted);
 void G_GPCupIntoRoundQueue(cupheader_t *cup, UINT8 setgametype, boolean setencore);
 
-extern INT16 kartmap2native[NEXTMAP_SPECIAL], nativemap2kart[NEXTMAP_SPECIAL];
-extern INT16 nextexnum;
+extern UINT16 kartmap2native[NEXTMAP_SPECIAL], nativemap2kart[NEXTMAP_SPECIAL];
+extern UINT16 nextexnum;
 
 extern INT32 gameovertics;
 extern UINT8 ammoremovaltics;
@@ -130,11 +130,11 @@ void weaponPrefChange4(void);
 
 #define MAXPLMOVE (50)
 
-const char *G_BuildMapName(INT32 map);
-INT32 G_MapNumber(const char *mapname);
-INT32 G_LevelTitleToMapNum(const char * leveltitle);
-INT16 G_KartMapToNative(INT16 mapnum);
-INT16 G_NativeMapToKart(INT16 mapnum);
+const char *G_BuildMapName(UINT16 map);
+UINT16 G_MapNumber(const char *mapname);
+UINT16 G_LevelTitleToMapNum(const char * leveltitle);
+UINT16 G_KartMapToNative(UINT16 mapnum);
+UINT16 G_NativeMapToKart(UINT16 mapnum);
 
 void G_ResetAnglePrediction(player_t *player);
 void G_BuildTiccmd(ticcmd_t *cmd, INT32 realtics, UINT8 ssplayer);
@@ -189,9 +189,9 @@ boolean G_AxisInDeadzone(UINT8 p, event_t *ev);
 void G_ChangePlayerReferences(mobj_t *oldmo, mobj_t *newmo);
 void G_DoReborn(INT32 playernum);
 void G_PlayerReborn(INT32 player, boolean betweenmaps);
-void G_InitNew(UINT8 pencoremode, INT32 map, boolean resetplayer,
+void G_InitNew(UINT8 pencoremode, UINT16 map, boolean resetplayer,
 	boolean skipprecutscene);
-char *G_BuildMapTitle(INT32 mapnum);
+char *G_BuildMapTitle(UINT16 mapnum);
 
 struct searchdim
 {
@@ -209,12 +209,12 @@ struct mapsearchfreq_t
 	UINT8  total;/* total hits */
 };
 
-INT32 G_FindMap(const char *query, char **foundmapnamep,
+UINT16 G_FindMap(const char *query, char **foundmapnamep,
 		mapsearchfreq_t **freqp, INT32 *freqc);
 void G_FreeMapSearch(mapsearchfreq_t *freq, INT32 freqc);
 
 /* Match map name by search + 2 digit map code or map number. */
-INT32 G_FindMapByNameOrCode(const char *query, char **foundmapnamep);
+UINT16 G_FindMapByNameOrCode(const char *query, char **foundmapnamep);
 
 // XMOD spawning
 mapthing_t *G_FindTeamStart(INT32 playernum);
@@ -226,7 +226,7 @@ void G_SpawnPlayer(INT32 playernum, boolean starpost);
 
 // Can be called by the startup code or M_Responder.
 // A normal game starts at map 1, but a warp test can start elsewhere
-void G_DeferedInitNew(boolean pencoremode, INT32 map, INT32 pickedchar,
+void G_DeferedInitNew(boolean pencoremode, UINT16 map, INT32 pickedchar,
 	UINT8 ssplayers, boolean FLS);
 void G_DoLoadLevel(boolean resetplayer);
 
@@ -235,11 +235,11 @@ void G_PreLevelTitleCard(void);
 boolean G_IsTitleCardAvailable(void);
 
 // Can be called by the startup code or M_Responder, calls P_SetupLevel.
-void G_LoadGame(UINT32 slot, INT16 mapoverride);
+void G_LoadGame(UINT32 slot, UINT16 mapoverride);
 
 void G_SaveGameData(void);
 
-void G_SaveGame(UINT32 slot, INT16 mapnum);
+void G_SaveGame(UINT32 slot, UINT16 mapnum);
 
 void G_SaveGameOver(UINT32 slot, boolean modifylives);
 
@@ -250,7 +250,7 @@ void G_UpdateGametypeSelections(void);
 INT32 G_GetGametypeByName(const char *gametypestr);
 INT32 G_GuessGametypeByTOL(UINT32 tol);
 
-boolean G_IsSpecialStage(INT32 mapnum);
+boolean G_IsSpecialStage(UINT16 mapnum);
 boolean G_GametypeUsesLives(void);
 boolean G_GametypeHasTeams(void);
 boolean G_GametypeHasSpectators(void);
@@ -381,7 +381,7 @@ maprecord_t *G_GetMapRecord(const char *mapname);
 maprecordpreset_t *G_AllocateMapRecordPreset(maprecord_t *record, const char *presetname, UINT8 version);
 maprecordpreset_t *G_GetMapRecordPreset(maprecord_t *record, const char *presetname);
 void G_ClearRecords(void);
-tic_t G_GetBestTime(INT16 map);
+tic_t G_GetBestTime(UINT16 map);
 boolean G_EmblemsEnabled(void);
 char *G_GetRecordReplayFolder(boolean home, boolean breaker);
 char *G_GetRecordReplay(const char *folder, UINT16 mapnum, UINT16 skinnum, recordreplay_e which);
@@ -398,7 +398,7 @@ UINT32 G_TOLFlag(INT32 pgametype);
 INT16 G_GetFirstMapOfGametype(UINT8 pgametype);
 
 INT16 G_RandMap(UINT32 tolflags, INT16 pprevmap, UINT8 ignorebuffer, UINT8 maphell, INT16 *extbuffer);
-void G_AddMapToBuffer(INT16 map);
+void G_AddMapToBuffer(UINT16 map);
 
 typedef struct 
 {
diff --git a/src/k_kart.c b/src/k_kart.c
index ecd2796dc..8071c1efb 100644
--- a/src/k_kart.c
+++ b/src/k_kart.c
@@ -6705,7 +6705,7 @@ static void K_RaceStart(player_t *player)
 
 }
 
-UINT8 K_RaceLapCount(INT16 mapNum)
+UINT8 K_RaceLapCount(UINT16 mapNum)
 {
 	if (!(gametypes[gametype]->rules & GTR_CIRCUIT))
 	{
diff --git a/src/k_kart.h b/src/k_kart.h
index b9e91772b..272222d5a 100644
--- a/src/k_kart.h
+++ b/src/k_kart.h
@@ -228,7 +228,7 @@ void K_SpawnBumpEffect(mobj_t *mo);
 void K_KartMoveAnimation(player_t *player);
 void K_KartPlayerHUDUpdate(player_t *player);
 void K_KartResetPlayerColor(player_t *player);
-UINT8 K_RaceLapCount(INT16 mapNum);
+UINT8 K_RaceLapCount(UINT16 mapNum);
 void K_KartPlayerThink(player_t *player, ticcmd_t *cmd);
 void K_KartPlayerAfterThink(player_t *player);
 angle_t K_MomentumAngle(mobj_t *mo);
diff --git a/src/lua_baselib.c b/src/lua_baselib.c
index cc30f2c64..78ac9d208 100644
--- a/src/lua_baselib.c
+++ b/src/lua_baselib.c
@@ -440,11 +440,11 @@ static int lib_pGetColorAfter(lua_State *L)
 static int lib_gMapNumber(lua_State *L)
 {
 	const char *arg = luaL_checkstring(L, 1);
-	INT32 map;
+	UINT16 map;
 
 	map = G_MapNumber(arg);
 
-	if (map == INT32_MAX)
+	if (map == NEXTMAP_INVALID)
 		return 0;
 
 
@@ -3347,7 +3347,7 @@ static int Lcheckmapnumber (lua_State *L, int idx, const char *fun)
 
 static int lib_gBuildMapName(lua_State *L)
 {
-	INT32 map = Lcheckmapnumber(L, 1, "G_BuildMapName");
+	UINT16 map = Lcheckmapnumber(L, 1, "G_BuildMapName");
 
 	if (lua_compatmode && map == 0) // v1 has undefined behaviour if you return 0, who knew.
 	{
@@ -3361,7 +3361,7 @@ static int lib_gBuildMapName(lua_State *L)
 
 static int lib_gBuildMapTitle(lua_State *L)
 {
-	INT32 map = Lcheckmapnumber(L, 1, "G_BuildMapTitle");
+	UINT16 map = Lcheckmapnumber(L, 1, "G_BuildMapTitle");
 	char *name;
 	if (map < 1 || map > nummapheaders)
 	{
@@ -3427,7 +3427,7 @@ static int lib_gFindMap(lua_State *L)
 {
 	const char *query = luaL_checkstring(L, 1);
 
-	INT32 map;
+	UINT16 map;
 	char *realname;
 	INT32 frc;
 	mapsearchfreq_t *frv;
@@ -3474,7 +3474,7 @@ Returns:
 static int lib_gFindMapByNameOrCode(lua_State *L)
 {
 	const char *query = luaL_checkstring(L, 1);
-	INT32 map;
+	UINT16 map;
 	char *realname;
 	map = G_FindMapByNameOrCode(query, &realname);
 	lua_pushnumber(L, map);
@@ -3542,7 +3542,7 @@ static int lib_gExitLevel(lua_State *L)
 
 static int lib_gIsSpecialStage(lua_State *L)
 {
-	INT32 mapnum = Lcheckmapnumber(L, 1, "G_IsSpecialStage");
+	UINT16 mapnum = Lcheckmapnumber(L, 1, "G_IsSpecialStage");
 	//HUDSAFE
 	INLEVEL
 	lua_pushboolean(L, G_IsSpecialStage(lua_compatmode ? G_KartMapToNative(mapnum) : mapnum));
diff --git a/src/lua_hudlib.c b/src/lua_hudlib.c
index 8fb09244a..153b548e1 100644
--- a/src/lua_hudlib.c
+++ b/src/lua_hudlib.c
@@ -1377,7 +1377,7 @@ static int libd_getStringColormap(lua_State *L)
 
 static int libd_getMapThumbnail(lua_State *L)
 {
-	INT16 mapnum;
+	UINT16 mapnum;
 	patch_t *patch = NULL;
 	HUDONLY
 	if (lua_type(L, 1) == LUA_TNUMBER)
@@ -1393,7 +1393,7 @@ static int libd_getMapThumbnail(lua_State *L)
 
 static int libd_getMapMinimap(lua_State *L)
 {
-	INT16 mapnum;
+	UINT16 mapnum;
 	patch_t *patch = NULL;
 	HUDONLY
 	if (lua_type(L, 1) == LUA_TNUMBER)
diff --git a/src/m_cond.c b/src/m_cond.c
index 83e7cb643..3454d2bcd 100644
--- a/src/m_cond.c
+++ b/src/m_cond.c
@@ -403,7 +403,7 @@ UINT8 M_SecretUnlocked(INT32 type)
 #undef CHADYES
 }
 
-UINT8 M_MapLocked(INT32 mapnum)
+UINT8 M_MapLocked(UINT16 mapnum)
 {
 
 #ifdef DEVELOP
@@ -517,9 +517,9 @@ INT32 M_UnlockableSkinNum(unlockable_t *unlock)
 // Pass -1 mapnum to continue from last emblem.
 // NULL if not found.
 // note that this goes in reverse!!
-emblem_t *M_GetLevelEmblems(INT32 mapnum)
+emblem_t *M_GetLevelEmblems(UINT16 mapnum)
 {
-	static INT32 map = -1;
+	static UINT16 map = -1;
 	static INT32 i = -1;
 
 	if (mapnum >= 0)
diff --git a/src/m_cond.h b/src/m_cond.h
index 087eae676..2c8d27d0b 100644
--- a/src/m_cond.h
+++ b/src/m_cond.h
@@ -170,11 +170,11 @@ UINT8 M_CheckLevelEmblems(void);
 // Checking unlockable status
 UINT8 M_AnySecretUnlocked(void);
 UINT8 M_SecretUnlocked(INT32 type);
-UINT8 M_MapLocked(INT32 mapnum);
+UINT8 M_MapLocked(UINT16 mapnum);
 INT32 M_CountEmblems(void);
 
 // Emblem shit
-emblem_t *M_GetLevelEmblems(INT32 mapnum);
+emblem_t *M_GetLevelEmblems(UINT16 mapnum);
 skincolornum_t M_GetEmblemColor(emblem_t *em);
 const char *M_GetEmblemPatch(emblem_t *em, boolean big);
 skincolornum_t M_GetExtraEmblemColor(extraemblem_t *em);
diff --git a/src/m_menu.c b/src/m_menu.c
index 865b25002..2a9f3bb7a 100644
--- a/src/m_menu.c
+++ b/src/m_menu.c
@@ -201,7 +201,7 @@ int  M_GetWaitingMode(void);
 
 typedef struct
 {
-	INT16 mapnum;
+	UINT16 mapnum;
 	char mapname[MAXMAPNAME];
 	UINT8 color;
 	boolean available;
@@ -637,10 +637,10 @@ INT32 HU_GetHighlightColor(void)
 	return highlightflags;
 }
 
-fixed_t M_GetMapThumbnail(INT16 mapnum, patch_t **out)
+fixed_t M_GetMapThumbnail(UINT16 mapnum, patch_t **out)
 {
 	patch_t *patch = NULL;
-	if (mapnum == -1)
+	if (mapnum == NEXTMAP_INVALID)
 		patch = randomlvl;
 	else if (mapnum >= 0 && mapnum < nummapheaders && mapheaderinfo[mapnum])
 		patch = mapheaderinfo[mapnum]->thumbnailPic;
@@ -2441,7 +2441,7 @@ static void M_CentreText(INT32 y, const char *string)
 //
 // used by pause & statistics to draw a row of emblems for a map
 //
-static void M_DrawMapEmblems(INT32 mapnum, INT32 x, INT32 y)
+static void M_DrawMapEmblems(UINT16 mapnum, INT32 x, INT32 y)
 {
 	UINT8 lasttype = UINT8_MAX, curtype;
 	emblem_t *emblem = M_GetLevelEmblems(mapnum);
@@ -2746,7 +2746,7 @@ static INT32 M_DrawMenuItem(menuitem_t *item, INT16 x, INT16 y, INT32 vflags, bo
 		{
 		case ITF_THUMBNAIL:
 		{
-			INT32 mapnum = G_MapNumber(item->patch);
+			UINT16 mapnum = G_MapNumber(item->patch);
 			scale = M_GetMapThumbnail(mapnum < nummapheaders ? mapnum : -1, &p)/4;
 			break;
 		}
@@ -3040,7 +3040,7 @@ static INT32 M_GetLevelListTOL(void)
 	}
 }
 
-static boolean M_LevelAvailableOnPlatter(INT32 mapnum)
+static boolean M_LevelAvailableOnPlatter(UINT16 mapnum)
 {
 	// don't care
 	(void)mapnum;
@@ -3052,7 +3052,7 @@ static boolean M_LevelAvailableOnPlatter(INT32 mapnum)
 //
 // Determines whether to show a given map in the various level-select lists.
 //
-static boolean M_CanShowLevelOnPlatter(INT32 mapnum)
+static boolean M_CanShowLevelOnPlatter(UINT16 mapnum)
 {
 	// Does the map exist?
 	if (mapnum < 0 || mapnum >= nummapheaders || !mapheaderinfo[mapnum])
@@ -3266,7 +3266,7 @@ static void M_UpdateLevelPlatterCups(void)
 				break;
 
 			levelselectmap_t *lsmap = &lsrow->maps[lsrow->numcolumns++];
-			INT16 mapnum = cup->cachedlevels[j];
+			UINT16 mapnum = cup->cachedlevels[j];
 
 			lsmap->mapnum = mapnum; // putting the map on the platter
 			lsmap->available = M_LevelAvailableOnPlatter(mapnum);
@@ -3351,7 +3351,7 @@ static void M_UpdateLevelPlatter(void)
 
 	for (i = 0; i < numsortedmaps; i++)
 	{
-		INT32 mapnum = sortedmaps[i];
+		UINT16 mapnum = sortedmaps[i];
 		mapheader_t *itermap = mapheaderinfo[mapnum];
 		boolean wide = false;//(headermap->menuflags & LF2_WIDEICON);
 
@@ -3882,7 +3882,7 @@ void MD_DrawLevelPlatterMenu(void)
 // Determines whether to show a given map in the various level-select lists.
 // Set gt = -1 to ignore gametype.
 //
-boolean M_CanShowLevelInList(INT32 mapnum)
+boolean M_CanShowLevelInList(UINT16 mapnum)
 {
 	return M_CanShowLevelOnPlatter(mapnum) && M_LevelAvailableOnPlatter(mapnum);
 }
@@ -6483,7 +6483,6 @@ INT32 MR_GrandPrixTemp(INT32 choice)
 INT32 MR_StartGrandPrix(INT32 choice)
 {
 	cupheader_t *gpcup;
-	INT32 levelNum;
 
 	(void)choice;
 
diff --git a/src/m_menu.h b/src/m_menu.h
index e7a6cb825..da24c74e9 100644
--- a/src/m_menu.h
+++ b/src/m_menu.h
@@ -129,7 +129,7 @@ typedef enum
 void M_QuitResponse(INT32 ch);
 
 // Determines whether to show a level in the list (platter version does not need to be exposed)
-boolean M_CanShowLevelInList(INT32 mapnum);
+boolean M_CanShowLevelInList(UINT16 mapnum);
 
 typedef enum
 {
@@ -450,7 +450,7 @@ void M_RefreshPauseMenu(void);
 
 INT32 HU_GetHighlightColor(void);
 
-fixed_t M_GetMapThumbnail(INT16 mapnum, patch_t **out);
+fixed_t M_GetMapThumbnail(UINT16 mapnum, patch_t **out);
 
 // Moviemode menu updating
 void Moviemode_option_Onchange(void);
diff --git a/src/p_saveg.c b/src/p_saveg.c
index 1ad790058..9c96bcca8 100644
--- a/src/p_saveg.c
+++ b/src/p_saveg.c
@@ -3997,7 +3997,7 @@ static inline void P_NetSyncSpecials(savebuffer_t *save)
 // =======================================================================
 //          Misc
 // =======================================================================
-static inline void P_ArchiveMisc(savebuffer_t *save, INT16 mapnum)
+static inline void P_ArchiveMisc(savebuffer_t *save, UINT16 mapnum)
 {
 	TracyCZone(__zone, true);
 
@@ -4007,20 +4007,20 @@ static inline void P_ArchiveMisc(savebuffer_t *save, INT16 mapnum)
 	if (gamecomplete)
 		mapnum |= 8192;
 
-	WRITEINT16(save->p, mapnum);
+	WRITEUINT16(save->p, mapnum);
 	WRITEUINT16(save->p, emeralds+357);
 	WRITESTRINGN(save->p, timeattackfolder, sizeof(timeattackfolder));
 
 	TracyCZoneEnd(__zone);
 }
 
-static inline void P_UnArchiveSPGame(savebuffer_t *save, INT16 mapoverride)
+static inline void P_UnArchiveSPGame(savebuffer_t *save, UINT16 mapoverride)
 {
 	TracyCZone(__zone, true);
 
 	char testname[sizeof(timeattackfolder)];
 
-	gamemap = READINT16(save->p);
+	gamemap = READUINT16(save->p);
 
 	if (mapoverride != 0)
 	{
@@ -4568,7 +4568,7 @@ static inline boolean P_UnArchiveLuabanksAndConsistency(savebuffer_t *save)
 	return ret;
 }
 
-void P_SaveGame(savebuffer_t *save, INT16 mapnum)
+void P_SaveGame(savebuffer_t *save, UINT16 mapnum)
 {
 	P_ArchiveMisc(save, mapnum);
 	P_ArchivePlayer(save);
@@ -4626,7 +4626,7 @@ void P_SaveNetGame(savebuffer_t *save, boolean resending)
 	TracyCZoneEnd(__zone);
 }
 
-boolean P_LoadGame(savebuffer_t *save, INT16 mapoverride)
+boolean P_LoadGame(savebuffer_t *save, UINT16 mapoverride)
 {
 	if (gamestate == GS_INTERMISSION)
 		Y_EndIntermission();
diff --git a/src/p_saveg.h b/src/p_saveg.h
index de0527dbe..ca4c6907b 100644
--- a/src/p_saveg.h
+++ b/src/p_saveg.h
@@ -27,9 +27,9 @@ extern "C" {
 // Persistent storage/archiving.
 // These are the load / save game routines.
 
-void P_SaveGame(savebuffer_t *save, INT16 mapnum);
+void P_SaveGame(savebuffer_t *save, UINT16 mapnum);
 void P_SaveNetGame(savebuffer_t *save, boolean resending);
-boolean P_LoadGame(savebuffer_t *save, INT16 mapoverride);
+boolean P_LoadGame(savebuffer_t *save, UINT16 mapoverride);
 boolean P_LoadNetGame(savebuffer_t *save, boolean reloading);
 
 mobj_t *P_FindNewPosition(UINT32 oldposition);
diff --git a/src/p_setup.c b/src/p_setup.c
index 79dbbf410..868cb1407 100644
--- a/src/p_setup.c
+++ b/src/p_setup.c
@@ -391,7 +391,7 @@ FUNCNORETURN static ATTRNORETURN void CorruptMapError(const char *msg)
   *
   * \param i The header to set flickies for
   */
-void P_SetDemoFlickies(INT16 i)
+void P_SetDemoFlickies(UINT16 i)
 {
 	mapheaderinfo[i]->numFlickies = 5;
 	mapheaderinfo[i]->flickies = Z_Realloc(mapheaderinfo[i]->flickies, 5*sizeof(mobjtype_t), PU_STATIC, NULL);
@@ -406,7 +406,7 @@ void P_SetDemoFlickies(INT16 i)
   *
   * \param i The header to clear flickies for
   */
-void P_DeleteFlickies(INT16 i)
+void P_DeleteFlickies(UINT16 i)
 {
 	if (mapheaderinfo[i]->flickies)
 		Z_Free(mapheaderinfo[i]->flickies);
@@ -486,7 +486,7 @@ static void P_ClearSingleMapHeaderInfo(INT16 num)
   *
   * \param i Index of header to allocate.
   */
-void P_AllocMapHeader(INT16 i)
+void P_AllocMapHeader(UINT16 i)
 {
 	if (i > nummapheaders)
 		I_Error("P_AllocMapHeader: Called on %d, should be %d", i, nummapheaders);
@@ -9394,7 +9394,7 @@ static lumpinfo_t* FindFolder(const char *folName, UINT16 *start, UINT16 *end, l
 }
 
 lumpnum_t wadnamelump = LUMPERROR;
-INT16 wadnamemap = 0; // gamemap based
+UINT16 wadnamemap = 0; // gamemap based
 
 // Initialising map data...
 UINT8 P_InitMapData(boolean existingmapheaders)
diff --git a/src/p_setup.h b/src/p_setup.h
index e09f467fa..7f0626dba 100644
--- a/src/p_setup.h
+++ b/src/p_setup.h
@@ -98,7 +98,7 @@ boolean P_AddWadFile(const char *wadfilename, wadcompat_t compat, boolean local)
 #define MAPRET_CURRENTREPLACED (1<<1)
 UINT8 P_InitMapData(boolean existingmapheaders);
 extern lumpnum_t wadnamelump;
-extern INT16 wadnamemap;
+extern UINT16 wadnamemap;
 #define WADNAMECHECK(name) (!strncmp(name, "WADNAME", 7))
 
 // WARNING: The following functions should be grouped as follows:
@@ -130,10 +130,10 @@ boolean P_ApplyLightOffset(UINT8 baselightnum, const sector_t *sector);
 boolean P_ApplyLightOffsetFine(UINT8 baselightlevel, const sector_t *sector);
 boolean P_SectorUsesDirectionalLighting(const sector_t *sector);
 size_t P_PrecacheLevelFlats(void);
-void P_AllocMapHeader(INT16 i);
+void P_AllocMapHeader(UINT16 i);
 
-void P_SetDemoFlickies(INT16 i);
-void P_DeleteFlickies(INT16 i);
+void P_SetDemoFlickies(UINT16 i);
+void P_DeleteFlickies(UINT16 i);
 
 // Needed for NiGHTS
 void P_ReloadRings(void);
diff --git a/src/p_user.c b/src/p_user.c
index dd57bc695..c4956d4f1 100644
--- a/src/p_user.c
+++ b/src/p_user.c
@@ -310,7 +310,7 @@ boolean P_PlayerMoving(INT32 pnum)
 //
 UINT8 P_GetNextEmerald(void)
 {
-	INT16 mapnum = gamemap-1;
+	UINT16 mapnum = gamemap-1;
 
 	if (mapnum > nummapheaders || !mapheaderinfo[mapnum])
 		return 0;
diff --git a/src/y_inter.c b/src/y_inter.c
index be1d7fe17..469119c84 100644
--- a/src/y_inter.c
+++ b/src/y_inter.c
@@ -1452,7 +1452,7 @@ void Y_VoteDrawer(void)
 	fixed_t rubyheight = 0;
 	fixed_t scale;
 	patch_t *pic;
-	INT16 mapnum;
+	UINT16 mapnum;
 	fixed_t picwidth = 160;
 
 	// CEP: scale by screen hypotenuse for extra voting rows
@@ -1551,7 +1551,7 @@ void Y_VoteDrawer(void)
 		if (i == rowval)
 		{
 			str = "RANDOM";
-			mapnum = -1;
+			mapnum = NEXTMAP_INVALID;
 		}
 		else
 		{