diff --git a/src/acs/call-funcs.cpp b/src/acs/call-funcs.cpp
index bde2125e2..eab3f6f85 100644
--- a/src/acs/call-funcs.cpp
+++ b/src/acs/call-funcs.cpp
@@ -3066,7 +3066,7 @@ bool CallFunc_MapWarp(ACSVM::Thread *thread, const ACSVM::Word *argV, ACSVM::Wor
 		return false;
 	}
 
-	nextmapoverride = (nextmap + 1);
+	nextmapoverride = (mapnum_t)(nextmap + 1);
 
 	if (argV[1] == 0)
 		skipstats = 1;
diff --git a/src/acs/environment.cpp b/src/acs/environment.cpp
index 41967d293..b83c875d4 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!
 	{
-		UINT16 mapnum = G_MapNumber(name->s->str);
+		mapnum_t mapnum = G_MapNumber(name->s->str);
 		if (mapnum < NEXTMAP_INVALID)
 			lumpnum = mapheaderinfo[mapnum]->lumpnum;
 	}
diff --git a/src/d_main.cpp b/src/d_main.cpp
index 0cd6991fb..1d1f0f298 100644
--- a/src/d_main.cpp
+++ b/src/d_main.cpp
@@ -15,6 +15,7 @@
 ///        plus functions to parse command line parameters, configure game
 ///        parameters, and call the startup functions.
 
+#include "g_mapnum.h"
 #if (defined (__unix__) && !defined (MSDOS)) || defined(__APPLE__) || defined (UNIXCOMMON)
 #include <sys/stat.h>
 #include <sys/types.h>
@@ -1172,7 +1173,7 @@ void D_StartTitle(void)
 			if (i > nummapheaders)
 				I_Error("D_StartTitle: No valid map ID found!?");
 
-			COM_BufAddText(va("map %s\n", G_BuildMapName(i)));
+			COM_BufAddText(va("map %s\n", G_BuildMapName((mapnum_t)(i))));
 		}
 
 		return;
@@ -1456,7 +1457,7 @@ void D_SRB2Main(void)
 {
 	INT32 p;
 
-	INT32 pstartmap = 1;
+	mapnum_t pstartmap = (mapnum_t)1;
 	boolean autostart = false;
 
 	/* break the version string into version numbers, for netplay */
@@ -2006,7 +2007,7 @@ void D_SRB2Main(void)
 	// rei/miru: bootmap (Idea: starts the game on a predefined map)
 	if (bootmap && !(M_CheckParm("-warp") && M_IsNextParm()))
 	{
-		pstartmap = G_MapNumber(bootmap)+1;
+		pstartmap = (mapnum_t)(G_MapNumber(bootmap)+1);
 
 		if (pstartmap > nummapheaders)
 		{
diff --git a/src/d_netcmd.c b/src/d_netcmd.c
index e08833fd8..f8797afcf 100644
--- a/src/d_netcmd.c
+++ b/src/d_netcmd.c
@@ -3340,7 +3340,7 @@ INT32 mapchangepending = 0;
   * \sa D_GameTypeChanged, Command_Map_f
   * \author Graue <graue@oceanbase.org>
   */
-void D_MapChange(UINT16 mapnum, INT32 newgametype, boolean pencoremode, boolean presetplayers, INT32 delay, boolean skipprecutscene, boolean pforcespecialstage)
+void D_MapChange(mapnum_t 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;
@@ -3412,7 +3412,7 @@ void D_SetupVote(void)
 	INT32 i;
 	UINT8 gt = (cv_kartgametypepreference.value == -1) ? gametype : cv_kartgametypepreference.value;
 	UINT8 secondgt = G_SometimesGetDifferentGametype(gt);
-	UINT16 votebuffer[4] = {NEXTMAP_INVALID,NEXTMAP_INVALID,NEXTMAP_INVALID,0};
+	mapnum_t votebuffer[4] = {NEXTMAP_INVALID,NEXTMAP_INVALID,NEXTMAP_INVALID,0};
 
 	if (cv_kartencore.value && cv_encorevotes.value == 1 && (gametypes[gt]->rules & GTR_CIRCUIT))
 		WRITEUINT8(p, (gt|VOTEMODIFIER_ENCORE));
@@ -3923,7 +3923,7 @@ static void Got_Mapcmd(UINT8 **cp, INT32 playernum)
 	UINT8 skipprecutscene, pforcespecialstage;
 	boolean pencoremode, hasroundqueuedata;
 	UINT16 lastgametype;
-	UINT16 mapnumber;
+	mapnum_t mapnumber;
 
 	forceresetplayers = deferencoremode = false;
 
diff --git a/src/d_netcmd.h b/src/d_netcmd.h
index 9ebbec6c9..2038284e6 100644
--- a/src/d_netcmd.h
+++ b/src/d_netcmd.h
@@ -16,6 +16,7 @@
 #define __D_NETCMD__
 
 #include "command.h"
+#include "g_mapnum.h"
 
 #ifdef __cplusplus
 extern "C" {
@@ -404,7 +405,7 @@ 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(UINT16 pmapnum, INT32 pgametype, boolean pencoremode, boolean presetplayers, INT32 pdelay, boolean pskipprecutscene, boolean pforcespecialstage);
+void D_MapChange(mapnum_t 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 247bb461a..1fc730ddb 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(UINT16 mapnum, const char *word)
+static mapheader_lighting_t *usemaplighting(mapnum_t 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, UINT16 mapnum, char *word2, f_vector3_t *vec, float min, float max)
+static void processvector(const char* name, mapnum_t 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, UINT16 mapnum, char *word2, f_vector
 }
 
 // Handle parsing globalefx info
-static void globalmapefxparameters(UINT16 mapnum, INT32 i, char *word, char *word2)
+static void globalmapefxparameters(mapnum_t 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);
 	}
 
-	UINT16 num = G_MapNumber(name);
+	mapnum_t 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 = (UINT16)G_MapNumber(word2);
+					unlockables[num].variable = 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 ae0e53fce..f39100745 100644
--- a/src/doomstat.h
+++ b/src/doomstat.h
@@ -23,6 +23,8 @@
 extern "C" {
 #endif
 
+#include "g_mapnum.h"
+
 // We need globally shared data structures, for defining the global state variables.
 #include "doomdata.h"
 
@@ -36,7 +38,7 @@ extern "C" {
 // =============================
 
 // Selected by user.
-extern UINT16 gamemap;
+extern mapnum_t gamemap;
 extern char mapmusname[7];
 extern UINT16 mapmusflags;
 extern UINT32 mapmusposition;
@@ -284,7 +286,7 @@ struct textprompt_t
 extern textprompt_t *textprompts[MAX_PROMPTS];
 
 // For the Custom Exit linedef.
-extern UINT16 nextmapoverride;
+extern mapnum_t nextmapoverride;
 extern UINT8 skipstats;
 
 // Fun extra stuff
@@ -347,7 +349,7 @@ struct cupheader_t
 
 	char icon[9];							///< Name of the icon patch
 	char *levellist[CUPCACHE_MAX];			///< List of levels that belong to this cup
-	UINT16 cachedlevels[CUPCACHE_MAX];		///< IDs in levellist, bonusgame, and specialstage
+	mapnum_t 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 5896a1365..cc312c14f 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
 
-UINT16 gamemap = 1;
+mapnum_t gamemap = 1;
 UINT32 maptol;
 
 preciptype_t globalweather = PRECIP_NONE;
@@ -179,7 +179,7 @@ boolean exitfadestarted = false;
 cutscene_t *cutscenes[128] = {};
 textprompt_t *textprompts[MAX_PROMPTS];
 
-UINT16 nextmapoverride;
+mapnum_t nextmapoverride;
 UINT8 skipstats;
 
 struct quake quake = {};
@@ -326,7 +326,7 @@ tic_t antibumptime; // Delay before players start bumping into one another.
 
 typedef struct
 {
-	UINT16 *mapbuffer;			// Pointer to zone memory
+	mapnum_t *mapbuffer;			// Pointer to zone memory
 	INT32 lastnummapheaders;	// Reset if nummapheaders != this
 	UINT8 counttogametype;		// Time to gametype change event
 } randmaps_t;
@@ -337,7 +337,7 @@ static void G_ResetRandMapBuffer(void)
 	INT32 i;
 	Z_Free(randmaps.mapbuffer);
 	randmaps.lastnummapheaders = nummapheaders;
-	randmaps.mapbuffer = Z_Malloc(randmaps.lastnummapheaders * sizeof(UINT16), PU_STATIC, NULL);
+	randmaps.mapbuffer = Z_Malloc(randmaps.lastnummapheaders * sizeof(mapnum_t), PU_STATIC, NULL);
 	for (i = 0; i < randmaps.lastnummapheaders; i++)
 		randmaps.mapbuffer[i] = NEXTMAP_INVALID;
 	//intentionally not resetting randmaps.counttogametype here
@@ -352,10 +352,10 @@ typedef struct joystickvector2_s
 	INT32 yaxis;
 } joystickvector2_t;
 
-UINT16 prevmap, nextmap;
+mapnum_t prevmap, nextmap;
 
-UINT16 kartmap2native[NEXTMAP_SPECIAL] = {0}, nativemap2kart[NEXTMAP_SPECIAL] = {0};
-UINT16 nextexnum = NUMMAPS;
+mapnum_t kartmap2native[NEXTMAP_SPECIAL] = {0}, nativemap2kart[NEXTMAP_SPECIAL] = {0};
+mapnum_t 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(UINT16 map)
+tic_t G_GetBestTime(mapnum_t 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(UINT16 map)
+const char *G_BuildMapName(mapnum_t map)
 {
 	if (map > 0 && map <= nummapheaders && mapheaderinfo[map - 1] != NULL)
 	{
@@ -1024,13 +1024,13 @@ const char *G_BuildMapName(UINT16 map)
   * \return Map number.
   * \sa G_BuildMapName, nextmapspecial_t
   */
-UINT16 G_MapNumber(const char * name)
+mapnum_t G_MapNumber(const char * name)
 {
 #ifdef NEXTMAPINSOC
 	if (strncasecmp("NEXTMAP_", name, 8) != 0)
 #endif
 	{
-		UINT16 map;
+		mapnum_t map;
 		UINT32 hash = FNV1a_QuickCaseHash(name, MAXMAPLUMPNAME);
 
 		for (map = 0; map < nummapheaders; ++map)
@@ -1067,9 +1067,9 @@ UINT16 G_MapNumber(const char * name)
   * \return Map number.
   * \sa G_BuildMapName, nextmapspecial_t
   */
-UINT16 G_LevelTitleToMapNum(const char * leveltitle)
+mapnum_t G_LevelTitleToMapNum(const char * leveltitle)
 {
-	UINT16  map;
+	mapnum_t  map;
 	char levelname[48];
 
 	for (map = 0; map < nummapheaders; ++map)
@@ -1103,7 +1103,7 @@ UINT16 G_LevelTitleToMapNum(const char * leveltitle)
 }
 
 // convert kart map number to native map number
-UINT16 G_KartMapToNative(UINT16 mapnum)
+mapnum_t G_KartMapToNative(mapnum_t mapnum)
 {
 	if (mapnum > 0 && mapnum < NEXTMAP_SPECIAL)
 		return kartmap2native[mapnum-1];
@@ -1111,7 +1111,7 @@ UINT16 G_KartMapToNative(UINT16 mapnum)
 }
 
 // convert native map number to kart
-UINT16 G_NativeMapToKart(UINT16 mapnum)
+mapnum_t G_NativeMapToKart(mapnum_t 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(UINT16 mapnum)
+boolean G_IsSpecialStage(mapnum_t mapnum)
 {
 	mapnum--; // gamemap-based to 0 indexed
 
@@ -4556,9 +4556,9 @@ UINT32 G_TOLFlag(INT32 pgametype)
 	return 0;
 }
 
-INT16 G_GetFirstMapOfGametype(UINT8 pgametype)
+mapnum_t G_GetFirstMapOfGametype(UINT8 pgametype)
 {
-	UINT16 mapnum = NEXTMAP_INVALID;
+	mapnum_t mapnum = NEXTMAP_INVALID;
 
 	/* G: not sure what to do with this
 	if ((gametypes[pgametype]->rules & GTR_CAMPAIGN) && kartcupheaders)
@@ -4619,12 +4619,12 @@ static INT32 TOLMaps(UINT8 pgametype)
   *         has those flags.
   * \author Graue <graue@oceanbase.org>
   */
-UINT16 G_RandMap(UINT32 tolflags, UINT16 pprevmap, UINT8 ignorebuffer, UINT8 maphell, UINT16 *extbuffer)
+mapnum_t G_RandMap(UINT32 tolflags, mapnum_t pprevmap, UINT8 ignorebuffer, UINT8 maphell, mapnum_t *extbuffer)
 {
 	UINT32 numokmaps = 0;
-	INT16 ix, bufx;
-	INT16 *okmaps = NULL;
-	UINT16 extbufsize = 0;
+	mapnum_t ix, bufx;
+	mapnum_t *okmaps = NULL;
+	mapnum_t extbufsize = 0;
 	boolean usehellmaps; // Only consider Hell maps in this pick
 
 	if (randmaps.lastnummapheaders != nummapheaders)
@@ -4772,10 +4772,10 @@ tryagain:
 	return ix;
 }
 
-void G_AddMapToBuffer(UINT16 map)
+void G_AddMapToBuffer(mapnum_t map)
 {
-	INT16 bufx;
-	INT16 refreshnum = (TOLMaps(gametype))-3;
+	mapnum_t bufx;
+	mapnum_t refreshnum = (TOLMaps(gametype))-3;
 
 	if (refreshnum < 0)
 		refreshnum = 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(UINT16 mapnum)
+static boolean CanSaveLevel(mapnum_t mapnum)
 {
 	// SRB2Kart: No save files yet
 	(void)mapnum;
@@ -5354,7 +5354,7 @@ static void G_DoCompleted(void)
 
 	S_StopSounds();
 
-	prevmap = (UINT16)(gamemap-1);
+	prevmap = (mapnum_t)(gamemap-1);
 
 	if (!demo.playback)
 	{
@@ -5613,7 +5613,7 @@ static boolean LoadLegacyRecords(savebuffer_t *save)
 	for (UINT32 i = 0; i < numgamedatamapheaders; i++)
 	{
 		char mapname[MAXMAPLUMPNAME];
-		//UINT16 mapnum;
+		//mapnum_t mapnum;
 		tic_t rectime;
 		tic_t reclap;
 
@@ -5987,7 +5987,7 @@ void G_SaveGameData(void)
 // G_InitFromSavegame
 // Can be called by the startup code or the menu task.
 //
-void G_LoadGame(UINT32 slot, UINT16 mapoverride)
+void G_LoadGame(UINT32 slot, mapnum_t mapoverride)
 {
 	char vcheck[VERSIONSIZE];
 	char savename[255];
@@ -6080,7 +6080,7 @@ void G_LoadGame(UINT32 slot, UINT16 mapoverride)
 // G_SaveGame
 // Saves your game.
 //
-void G_SaveGame(UINT32 slot, UINT16 mapnum)
+void G_SaveGame(UINT32 slot, mapnum_t mapnum)
 {
 	boolean saved;
 	char savename[256] = "";
@@ -6242,7 +6242,7 @@ cleanup:
 // Can be called by the startup code or the menu task,
 // consoleplayer, displayplayers[], playeringame[] should be set.
 //
-void G_DeferedInitNew(boolean pencoremode, UINT16 map, INT32 pickedchar, UINT8 ssplayers, boolean FLS)
+void G_DeferedInitNew(boolean pencoremode, mapnum_t map, INT32 pickedchar, UINT8 ssplayers, boolean FLS)
 {
 	UINT16 color = SKINCOLOR_NONE;
 	INT32 dogametype;
@@ -6289,7 +6289,7 @@ void G_DeferedInitNew(boolean pencoremode, UINT16 map, INT32 pickedchar, UINT8 s
 // This is the map command interpretation something like Command_Map_f
 //
 // called at: map cmd execution, doloadgame, doplaydemo
-void G_InitNew(UINT8 pencoremode, UINT16 map, boolean resetplayer, boolean skipprecutscene)
+void G_InitNew(UINT8 pencoremode, mapnum_t map, boolean resetplayer, boolean skipprecutscene)
 {
 	const char * mapname = G_BuildMapName(map);
 
@@ -6390,7 +6390,7 @@ void G_InitNew(UINT8 pencoremode, UINT16 map, boolean resetplayer, boolean skipp
 }
 
 
-char *G_BuildMapTitle(UINT16 mapnum)
+char *G_BuildMapTitle(mapnum_t mapnum)
 {
 	char *title = NULL;
 
@@ -6463,7 +6463,7 @@ static void measurekeywords(mapsearchfreq_t *fr,
 }
 
 static void writesimplefreq(mapsearchfreq_t *fr, INT32 *frc,
-		UINT16 mapnum, UINT8 pos, UINT8 siz)
+		mapnum_t mapnum, UINT8 pos, UINT8 siz)
 {
 	fr[(*frc)].mapnum = mapnum;
 	fr[(*frc)].matchd = ZZ_Alloc(sizeof (struct searchdim));
@@ -6474,12 +6474,12 @@ static void writesimplefreq(mapsearchfreq_t *fr, INT32 *frc,
 	(*frc)++;
 }
 
-UINT16 G_FindMap(const char *mapname, char **foundmapnamep,
+mapnum_t G_FindMap(const char *mapname, char **foundmapnamep,
 		mapsearchfreq_t **freqp, INT32 *freqcp)
 {
-	UINT16 newmapnum = 0;
-	UINT16 mapnum;
-	UINT16 apromapnum = 0;
+	mapnum_t newmapnum = 0;
+	mapnum_t mapnum;
+	mapnum_t apromapnum = 0;
 
 	size_t      mapnamelen;
 	char   *realmapname = NULL;
@@ -6612,9 +6612,9 @@ void G_FreeMapSearch(mapsearchfreq_t *freq, INT32 freqc)
 	Z_Free(freq);
 }
 
-UINT16 G_FindMapByNameOrCode(const char *mapname, char **realmapnamep)
+mapnum_t G_FindMapByNameOrCode(const char *mapname, char **realmapnamep)
 {
-	INT32 newmapnum;
+	mapnum_t newmapnum;
 
 	size_t mapnamelen;
 
diff --git a/src/g_game.h b/src/g_game.h
index b86f7d748..a42a90c5e 100644
--- a/src/g_game.h
+++ b/src/g_game.h
@@ -14,6 +14,7 @@
 #ifndef __G_GAME__
 #define __G_GAME__
 
+#include "g_mapnum.h"
 #include "doomdef.h"
 #include "doomstat.h"
 #include "d_event.h"
@@ -38,20 +39,7 @@ extern boolean playeringame[MAXPLAYERS];
 extern tic_t levelstarttic;
 
 // for modding?
-extern UINT16 prevmap, nextmap;
-
-// see also G_MapNumber
-typedef enum
-{
-	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;
+extern mapnum_t prevmap, nextmap;
 
 #define ROUNDQUEUE_MAX 10 // sane max? maybe make dynamically allocated later
 #define ROUNDQUEUE_CLEAR UINT16_MAX // lives in gametype field of packets
@@ -77,8 +65,8 @@ 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 UINT16 kartmap2native[NEXTMAP_SPECIAL], nativemap2kart[NEXTMAP_SPECIAL];
-extern UINT16 nextexnum;
+extern mapnum_t kartmap2native[NEXTMAP_SPECIAL], nativemap2kart[NEXTMAP_SPECIAL];
+extern mapnum_t nextexnum;
 
 extern INT32 gameovertics;
 extern UINT8 ammoremovaltics;
@@ -130,11 +118,11 @@ void weaponPrefChange4(void);
 
 #define MAXPLMOVE (50)
 
-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);
+const char *G_BuildMapName(mapnum_t map);
+mapnum_t G_MapNumber(const char *mapname);
+mapnum_t G_LevelTitleToMapNum(const char * leveltitle);
+mapnum_t G_KartMapToNative(mapnum_t mapnum);
+mapnum_t G_NativeMapToKart(mapnum_t mapnum);
 
 void G_ResetAnglePrediction(player_t *player);
 void G_BuildTiccmd(ticcmd_t *cmd, INT32 realtics, UINT8 ssplayer);
@@ -189,9 +177,9 @@ 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, UINT16 map, boolean resetplayer,
+void G_InitNew(UINT8 pencoremode, mapnum_t map, boolean resetplayer,
 	boolean skipprecutscene);
-char *G_BuildMapTitle(UINT16 mapnum);
+char *G_BuildMapTitle(mapnum_t mapnum);
 
 struct searchdim
 {
@@ -209,12 +197,12 @@ struct mapsearchfreq_t
 	UINT8  total;/* total hits */
 };
 
-UINT16 G_FindMap(const char *query, char **foundmapnamep,
+mapnum_t 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. */
-UINT16 G_FindMapByNameOrCode(const char *query, char **foundmapnamep);
+mapnum_t G_FindMapByNameOrCode(const char *query, char **foundmapnamep);
 
 // XMOD spawning
 mapthing_t *G_FindTeamStart(INT32 playernum);
@@ -226,7 +214,7 @@ 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, UINT16 map, INT32 pickedchar,
+void G_DeferedInitNew(boolean pencoremode, mapnum_t map, INT32 pickedchar,
 	UINT8 ssplayers, boolean FLS);
 void G_DoLoadLevel(boolean resetplayer);
 
@@ -235,11 +223,11 @@ 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, UINT16 mapoverride);
+void G_LoadGame(UINT32 slot, mapnum_t mapoverride);
 
 void G_SaveGameData(void);
 
-void G_SaveGame(UINT32 slot, UINT16 mapnum);
+void G_SaveGame(UINT32 slot, mapnum_t mapnum);
 
 void G_SaveGameOver(UINT32 slot, boolean modifylives);
 
@@ -250,7 +238,7 @@ void G_UpdateGametypeSelections(void);
 INT32 G_GetGametypeByName(const char *gametypestr);
 INT32 G_GuessGametypeByTOL(UINT32 tol);
 
-boolean G_IsSpecialStage(UINT16 mapnum);
+boolean G_IsSpecialStage(mapnum_t mapnum);
 boolean G_GametypeUsesLives(void);
 boolean G_GametypeHasTeams(void);
 boolean G_GametypeHasSpectators(void);
@@ -381,11 +369,11 @@ 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(UINT16 map);
+tic_t G_GetBestTime(mapnum_t 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);
-boolean G_CheckRecordReplay(const char *folder, UINT16 mapnum, UINT16 skinnum, recordreplay_e which);
+char *G_GetRecordReplay(const char *folder, mapnum_t mapnum, UINT16 skinnum, recordreplay_e which);
+boolean G_CheckRecordReplay(const char *folder, mapnum_t mapnum, UINT16 skinnum, recordreplay_e which);
 
 FUNCMATH INT32 G_TicsToHours(tic_t tics);
 FUNCMATH INT32 G_TicsToMinutes(tic_t tics, boolean full);
@@ -395,10 +383,10 @@ FUNCMATH INT32 G_TicsToMilliseconds(tic_t tics);
 
 // Don't split up TOL handling
 UINT32 G_TOLFlag(INT32 pgametype);
-INT16 G_GetFirstMapOfGametype(UINT8 pgametype);
+mapnum_t G_GetFirstMapOfGametype(UINT8 pgametype);
 
-UINT16 G_RandMap(UINT32 tolflags, UINT16 pprevmap, UINT8 ignorebuffer, UINT8 maphell, UINT16 *extbuffer);
-void G_AddMapToBuffer(UINT16 map);
+mapnum_t G_RandMap(UINT32 tolflags, mapnum_t pprevmap, UINT8 ignorebuffer, UINT8 maphell, mapnum_t *extbuffer);
+void G_AddMapToBuffer(mapnum_t map);
 
 typedef struct 
 {
diff --git a/src/g_mapnum.h b/src/g_mapnum.h
new file mode 100644
index 000000000..fe761e4cb
--- /dev/null
+++ b/src/g_mapnum.h
@@ -0,0 +1,38 @@
+// BLANKART
+//-----------------------------------------------------------------------------
+// Copyright (C) 2026 by Team BlanKart.
+//
+// This program is free software distributed under the
+// terms of the GNU General Public License, version 2.
+// See the 'LICENSE' file for more details.
+//-----------------------------------------------------------------------------
+/// \file  d_player.h
+/// \brief Map number type
+
+#ifndef __MAPNUM__
+#define __MAPNUM__
+
+#include "doomdef.h"
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+// see also G_MapNumber
+typedef enum
+{
+    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
+} ATTRPACK mapnum_t;
+
+#ifdef __cplusplus
+} // extern "C"
+#endif
+
+#endif
diff --git a/src/k_kart.c b/src/k_kart.c
index 8071c1efb..48b3f93c0 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(UINT16 mapNum)
+UINT8 K_RaceLapCount(mapnum_t mapNum)
 {
 	if (!(gametypes[gametype]->rules & GTR_CIRCUIT))
 	{
diff --git a/src/k_kart.h b/src/k_kart.h
index 272222d5a..76c70cbdf 100644
--- a/src/k_kart.h
+++ b/src/k_kart.h
@@ -9,6 +9,7 @@
 #include "doomdef.h"
 #include "d_player.h" // Need for player_t
 #include "command.h" // Need for player_t
+#include "g_game.h" // Need for mapnum_t
 
 #ifdef __cplusplus
 extern "C" {
@@ -228,7 +229,7 @@ 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(UINT16 mapNum);
+UINT8 K_RaceLapCount(mapnum_t 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 1cb9f7202..079777626 100644
--- a/src/lua_baselib.c
+++ b/src/lua_baselib.c
@@ -440,7 +440,7 @@ static int lib_pGetColorAfter(lua_State *L)
 static int lib_gMapNumber(lua_State *L)
 {
 	const char *arg = luaL_checkstring(L, 1);
-	UINT16 map;
+	mapnum_t map;
 
 	map = G_MapNumber(arg);
 
@@ -3347,7 +3347,7 @@ static int Lcheckmapnumber (lua_State *L, int idx, const char *fun)
 
 static int lib_gBuildMapName(lua_State *L)
 {
-	UINT16 map = Lcheckmapnumber(L, 1, "G_BuildMapName");
+	mapnum_t 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)
 {
-	UINT16 map = Lcheckmapnumber(L, 1, "G_BuildMapTitle");
+	mapnum_t 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);
 
-	UINT16 map;
+	mapnum_t 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);
-	UINT16 map;
+	mapnum_t map;
 	char *realname;
 	map = G_FindMapByNameOrCode(query, &realname);
 	lua_pushnumber(L, map);
@@ -3519,7 +3519,7 @@ static int lib_gSetCustomExitVars(lua_State *L)
 
 	if (n >= 1)
 	{
-		nextmapoverride = (UINT16)luaL_optinteger(L, 1, 0);
+		nextmapoverride = luaL_optinteger(L, 1, 0);
 		skipstats = (INT16)luaL_optinteger(L, 2, 0);
 		if (lua_compatmode && nextmapoverride)
 			nextmapoverride = G_KartMapToNative(nextmapoverride);
@@ -3542,7 +3542,7 @@ static int lib_gExitLevel(lua_State *L)
 
 static int lib_gIsSpecialStage(lua_State *L)
 {
-	UINT16 mapnum = Lcheckmapnumber(L, 1, "G_IsSpecialStage");
+	mapnum_t 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 153b548e1..e564b80e1 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)
 {
-	UINT16 mapnum;
+	mapnum_t 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)
 {
-	UINT16 mapnum;
+	mapnum_t 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 3454d2bcd..d157b022f 100644
--- a/src/m_cond.c
+++ b/src/m_cond.c
@@ -403,13 +403,13 @@ UINT8 M_SecretUnlocked(INT32 type)
 #undef CHADYES
 }
 
-UINT8 M_MapLocked(UINT16 mapnum)
+UINT8 M_MapLocked(mapnum_t mapnum)
 {
 
 #ifdef DEVELOP
 	if (1)
 		return false;
-#endif	
+#endif
 	if (!mapnum || mapnum > nummapheaders)
 		return false;
 	if (!mapheaderinfo[mapnum-1] || mapheaderinfo[mapnum-1]->unlockrequired < 0)
@@ -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(UINT16 mapnum)
+emblem_t *M_GetLevelEmblems(mapnum_t mapnum)
 {
-	static UINT16 map = -1;
+	static mapnum_t map = NEXTMAP_INVALID;
 	static INT32 i = -1;
 
 	if (mapnum >= 0)
diff --git a/src/m_cond.h b/src/m_cond.h
index 2c8d27d0b..fb31299aa 100644
--- a/src/m_cond.h
+++ b/src/m_cond.h
@@ -14,6 +14,7 @@
 #define __M_COND_H__
 
 #include "info.h"
+#include "g_mapnum.h"
 
 #ifdef __cplusplus
 extern "C" {
@@ -170,11 +171,11 @@ UINT8 M_CheckLevelEmblems(void);
 // Checking unlockable status
 UINT8 M_AnySecretUnlocked(void);
 UINT8 M_SecretUnlocked(INT32 type);
-UINT8 M_MapLocked(UINT16 mapnum);
+UINT8 M_MapLocked(mapnum_t mapnum);
 INT32 M_CountEmblems(void);
 
 // Emblem shit
-emblem_t *M_GetLevelEmblems(UINT16 mapnum);
+emblem_t *M_GetLevelEmblems(mapnum_t 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 473529cb4..7353858a6 100644
--- a/src/m_menu.c
+++ b/src/m_menu.c
@@ -201,7 +201,7 @@ int  M_GetWaitingMode(void);
 
 typedef struct
 {
-	UINT16 mapnum;
+	mapnum_t mapnum;
 	char mapname[MAXMAPNAME];
 	UINT8 color;
 	boolean available;
@@ -637,7 +637,7 @@ INT32 HU_GetHighlightColor(void)
 	return highlightflags;
 }
 
-fixed_t M_GetMapThumbnail(UINT16 mapnum, patch_t **out)
+fixed_t M_GetMapThumbnail(mapnum_t mapnum, patch_t **out)
 {
 	patch_t *patch = NULL;
 	if (mapnum == NEXTMAP_INVALID)
@@ -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(UINT16 mapnum, INT32 x, INT32 y)
+static void M_DrawMapEmblems(mapnum_t 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:
 		{
-			UINT16 mapnum = G_MapNumber(item->patch);
+			mapnum_t mapnum = G_MapNumber(item->patch);
 			scale = M_GetMapThumbnail(mapnum < nummapheaders ? mapnum : NEXTMAP_INVALID, &p)/4;
 			break;
 		}
@@ -3040,7 +3040,7 @@ static INT32 M_GetLevelListTOL(void)
 	}
 }
 
-static boolean M_LevelAvailableOnPlatter(UINT16 mapnum)
+static boolean M_LevelAvailableOnPlatter(mapnum_t mapnum)
 {
 	// don't care
 	(void)mapnum;
@@ -3052,7 +3052,7 @@ static boolean M_LevelAvailableOnPlatter(UINT16 mapnum)
 //
 // Determines whether to show a given map in the various level-select lists.
 //
-static boolean M_CanShowLevelOnPlatter(UINT16 mapnum)
+static boolean M_CanShowLevelOnPlatter(mapnum_t 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++];
-			UINT16 mapnum = cup->cachedlevels[j];
+			mapnum_t 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++)
 	{
-		UINT16 mapnum = sortedmaps[i];
+		mapnum_t 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(UINT16 mapnum)
+boolean M_CanShowLevelInList(mapnum_t mapnum)
 {
 	return M_CanShowLevelOnPlatter(mapnum) && M_LevelAvailableOnPlatter(mapnum);
 }
diff --git a/src/m_menu.h b/src/m_menu.h
index da24c74e9..243f8ec08 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(UINT16 mapnum);
+boolean M_CanShowLevelInList(mapnum_t mapnum);
 
 typedef enum
 {
@@ -450,7 +450,7 @@ void M_RefreshPauseMenu(void);
 
 INT32 HU_GetHighlightColor(void);
 
-fixed_t M_GetMapThumbnail(UINT16 mapnum, patch_t **out);
+fixed_t M_GetMapThumbnail(mapnum_t 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 9c96bcca8..03eb9119b 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, UINT16 mapnum)
+static inline void P_ArchiveMisc(savebuffer_t *save, mapnum_t mapnum)
 {
 	TracyCZone(__zone, true);
 
@@ -4014,7 +4014,7 @@ static inline void P_ArchiveMisc(savebuffer_t *save, UINT16 mapnum)
 	TracyCZoneEnd(__zone);
 }
 
-static inline void P_UnArchiveSPGame(savebuffer_t *save, UINT16 mapoverride)
+static inline void P_UnArchiveSPGame(savebuffer_t *save, mapnum_t mapoverride)
 {
 	TracyCZone(__zone, true);
 
@@ -4568,7 +4568,7 @@ static inline boolean P_UnArchiveLuabanksAndConsistency(savebuffer_t *save)
 	return ret;
 }
 
-void P_SaveGame(savebuffer_t *save, UINT16 mapnum)
+void P_SaveGame(savebuffer_t *save, mapnum_t 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, UINT16 mapoverride)
+boolean P_LoadGame(savebuffer_t *save, mapnum_t mapoverride)
 {
 	if (gamestate == GS_INTERMISSION)
 		Y_EndIntermission();
diff --git a/src/p_saveg.h b/src/p_saveg.h
index ca4c6907b..e2216ce13 100644
--- a/src/p_saveg.h
+++ b/src/p_saveg.h
@@ -14,6 +14,8 @@
 #ifndef __P_SAVEG__
 #define __P_SAVEG__
 
+#include "g_mapnum.h"
+
 #ifdef __cplusplus
 extern "C" {
 #endif
@@ -27,9 +29,9 @@ extern "C" {
 // Persistent storage/archiving.
 // These are the load / save game routines.
 
-void P_SaveGame(savebuffer_t *save, UINT16 mapnum);
+void P_SaveGame(savebuffer_t *save, mapnum_t mapnum);
 void P_SaveNetGame(savebuffer_t *save, boolean resending);
-boolean P_LoadGame(savebuffer_t *save, UINT16 mapoverride);
+boolean P_LoadGame(savebuffer_t *save, mapnum_t 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 868cb1407..e8848937a 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(UINT16 i)
+void P_SetDemoFlickies(mapnum_t 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(UINT16 i)
   *
   * \param i The header to clear flickies for
   */
-void P_DeleteFlickies(UINT16 i)
+void P_DeleteFlickies(mapnum_t 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(UINT16 i)
+void P_AllocMapHeader(mapnum_t 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;
-UINT16 wadnamemap = 0; // gamemap based
+mapnum_t 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 7f0626dba..4fb4fc10c 100644
--- a/src/p_setup.h
+++ b/src/p_setup.h
@@ -14,6 +14,7 @@
 #ifndef __P_SETUP__
 #define __P_SETUP__
 
+#include "g_mapnum.h"
 #include "doomdata.h"
 #include "doomstat.h"
 #include "r_defs.h"
@@ -98,7 +99,7 @@ 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 UINT16 wadnamemap;
+extern mapnum_t wadnamemap;
 #define WADNAMECHECK(name) (!strncmp(name, "WADNAME", 7))
 
 // WARNING: The following functions should be grouped as follows:
@@ -130,10 +131,10 @@ 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(UINT16 i);
+void P_AllocMapHeader(mapnum_t i);
 
-void P_SetDemoFlickies(UINT16 i);
-void P_DeleteFlickies(UINT16 i);
+void P_SetDemoFlickies(mapnum_t i);
+void P_DeleteFlickies(mapnum_t i);
 
 // Needed for NiGHTS
 void P_ReloadRings(void);
diff --git a/src/p_spec.c b/src/p_spec.c
index d3d02dd29..c596fa5d4 100644
--- a/src/p_spec.c
+++ b/src/p_spec.c
@@ -5286,7 +5286,7 @@ static void P_ProcessExitSector(player_t *player, mtag_t sectag)
 		return;
 	}
 
-	nextmapoverride = (UINT16)(udmf ? lines[lineindex].args[0] : lines[lineindex].frontsector->floorheight>>FRACBITS);
+	nextmapoverride = (mapnum_t)(udmf ? lines[lineindex].args[0] : lines[lineindex].frontsector->floorheight>>FRACBITS);
 
 	if (lines[lineindex].args[1] & TMEF_SKIPTALLY)
 		skipstats = 1;
diff --git a/src/p_user.c b/src/p_user.c
index c4956d4f1..f2f6a34e3 100644
--- a/src/p_user.c
+++ b/src/p_user.c
@@ -310,7 +310,7 @@ boolean P_PlayerMoving(INT32 pnum)
 //
 UINT8 P_GetNextEmerald(void)
 {
-	UINT16 mapnum = gamemap-1;
+	mapnum_t mapnum = gamemap-1;
 
 	if (mapnum > nummapheaders || !mapheaderinfo[mapnum])
 		return 0;
diff --git a/src/y_inter.c b/src/y_inter.c
index 469119c84..65ba56a24 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;
-	UINT16 mapnum;
+	mapnum_t mapnum;
 	fixed_t picwidth = 160;
 
 	// CEP: scale by screen hypotenuse for extra voting rows