diff --git a/source/build/include/build.h b/source/build/include/build.h
index 565535596..d566b9522 100644
--- a/source/build/include/build.h
+++ b/source/build/include/build.h
@@ -317,6 +317,9 @@ enum {
     SPR_ALIGN_MASK = 32+16,
 };
 
+// compatibility token for bitfield uses of the most significant bit of signed int16_t
+#define INT16_32768 ((int16_t)32768)
+
 #include "buildtypes.h"
 #define UNTRACKED_STRUCTS
 #undef buildtypes_h__
diff --git a/source/build/include/buildtypes.h b/source/build/include/buildtypes.h
index 55d31b01d..351589e97 100644
--- a/source/build/include/buildtypes.h
+++ b/source/build/include/buildtypes.h
@@ -50,7 +50,7 @@ typedef struct
     StructTracker(Sector, int8_t) floorshade;
     StructTracker(Sector, uint8_t) floorpal, floorxpanning, floorypanning;
     StructTracker(Sector, uint8_t) /*CM_CEILINGZ:*/ visibility, fogpal;
-    StructTracker(Sector, uint16_t) lotag, hitag;
+    StructTracker(Sector, int16_t) lotag, hitag;
     StructTracker(Sector, int16_t) extra;
 } StructName(sectortypev7);
 
@@ -77,7 +77,7 @@ typedef struct
     StructTracker(Wall, int16_t) picnum, overpicnum;
     StructTracker(Wall, int8_t) shade;
     StructTracker(Wall, uint8_t) pal, xrepeat, yrepeat, xpanning, ypanning;
-    StructTracker(Wall, uint16_t) lotag, hitag;
+    StructTracker(Wall, int16_t) lotag, hitag;
     StructTracker(Wall, int16_t) extra;
 } StructName(walltypev7);
 
@@ -114,7 +114,7 @@ typedef struct
     StructTracker(Sprite, int8_t) xoffset, yoffset;
     StructTracker(Sprite, int16_t) sectnum, statnum;
     StructTracker(Sprite, int16_t) ang, owner, xvel, yvel, zvel;
-    StructTracker(Sprite, uint16_t) lotag, hitag;
+    StructTracker(Sprite, int16_t) lotag, hitag;
     StructTracker(Sprite, int16_t) extra;
 } StructName(spritetype);
 
@@ -140,7 +140,7 @@ typedef struct
     StructTracker(Sector, uint8_t) floorpal, floorxpanning, floorypanning;
 
     StructTracker(Sector, uint8_t) /*CM_CEILINGZ:*/ visibility, fogpal;
-    StructTracker(Sector, uint16_t) lotag, hitag;
+    StructTracker(Sector, int16_t) lotag, hitag;
     StructTracker(Sector, int16_t) extra;
 } StructName(sectortypevx);
 
@@ -154,7 +154,7 @@ typedef struct
     StructTracker(Wall, int16_t) picnum, overpicnum;
     StructTracker(Wall, int8_t) shade;
     StructTracker(Wall, uint8_t) pal, xrepeat, yrepeat, xpanning, ypanning;
-    StructTracker(Wall, uint16_t) lotag, hitag;
+    StructTracker(Wall, int16_t) lotag, hitag;
     StructTracker(Wall, int16_t) extra;
     StructTracker(Wall, uint8_t) blend, filler_;
 } StructName(walltypevx);
diff --git a/source/duke3d/src/actors.cpp b/source/duke3d/src/actors.cpp
index 7e6002428..65ebd5499 100644
--- a/source/duke3d/src/actors.cpp
+++ b/source/duke3d/src/actors.cpp
@@ -2123,7 +2123,7 @@ crack_default:
                     {
                         pSprite->lotag -= 3;
                         if ((int16_t)pSprite->lotag <= 0)
-                            pSprite->lotag = (uint16_t)(-99);
+                            pSprite->lotag = -99;
                     }
                     else
                         pSprite->shade = -33;
@@ -5656,7 +5656,7 @@ ACTOR_STATIC void G_MoveEffectors(void)   //STATNUM 3
 
             j = pSprite->owner;
 
-            if (sprite[j].lotag == UINT16_MAX)
+            if ((uint16_t)sprite[j].lotag == UINT16_MAX)
                 DELETE_SPRITE_AND_CONTINUE(spriteNum);
 
             q = pSector->extra>>3;
@@ -6499,7 +6499,7 @@ ACTOR_STATIC void G_MoveEffectors(void)   //STATNUM 3
 
         case SE_10_DOOR_AUTO_CLOSE:
             // XXX: 32791, what the hell?
-            if ((pSector->lotag&0xff) == ST_27_STRETCH_BRIDGE || (pSector->floorz > pSector->ceilingz && (pSector->lotag&0xff) != ST_23_SWINGING_DOOR) || pSector->lotag == 32791)
+            if ((pSector->lotag&0xff) == ST_27_STRETCH_BRIDGE || (pSector->floorz > pSector->ceilingz && (pSector->lotag&0xff) != ST_23_SWINGING_DOOR) || pSector->lotag == (int16_t)32791)
             {
                 j = 1;
 
diff --git a/source/duke3d/src/game.cpp b/source/duke3d/src/game.cpp
index e2cd240c2..b34be2224 100644
--- a/source/duke3d/src/game.cpp
+++ b/source/duke3d/src/game.cpp
@@ -1272,7 +1272,7 @@ static int32_t G_InitActor(int32_t i, int32_t tilenum, int32_t set_movflag_uncon
     {
         // ^^^ C-CON takes precedence for now.
         const el_actor_t *a = &g_elActors[tilenum];
-        uint16_t *movflagsptr = &AC_MOVFLAGS(&sprite[i], &actor[i]);
+        auto movflagsptr = &AC_MOVFLAGS(&sprite[i], &actor[i]);
 
         SH(i) = a->strength;
         AC_ACTION_ID(actor[i].t_data) = a->act.id;
@@ -3116,7 +3116,7 @@ int A_Spawn(int spriteNum, int tileNum)
             case SE_9_DOWN_OPEN_DOOR_LIGHTS:
                 if (sector[sectNum].lotag &&
                         labs(sector[sectNum].ceilingz-pSprite->z) > 1024)
-                    sector[sectNum].lotag |= 32768; //If its open
+                    sector[sectNum].lotag |= INT16_32768; //If its open
                 fallthrough__;
             case SE_8_UP_OPEN_DOOR_LIGHTS:
                 //First, get the ceiling-floor shade
@@ -3210,7 +3210,7 @@ int A_Spawn(int spriteNum, int tileNum)
                     int const startWall = sector[sectNum].wallptr;
                     int const endWall   = startWall + sector[sectNum].wallnum;
 
-                    pSprite->extra = (sector[sectNum].hitag != UINT16_MAX);
+                    pSprite->extra = ((uint16_t)sector[sectNum].hitag != UINT16_MAX);
 
                     // TRAIN_SECTOR_TO_SE_INDEX
                     sector[sectNum].hitag = newSprite;
diff --git a/source/duke3d/src/gameexec.cpp b/source/duke3d/src/gameexec.cpp
index 3065f5cd2..80c424335 100644
--- a/source/duke3d/src/gameexec.cpp
+++ b/source/duke3d/src/gameexec.cpp
@@ -261,7 +261,7 @@ static int32_t VM_CheckSquished(void)
 #endif
 
     if (vm.pSprite->pal == 1 ?
-        (floorZ - ceilZ >= ZOFFSET5 || (pSector->lotag&32768)) :
+        (floorZ - ceilZ >= ZOFFSET5 || (pSector->lotag & INT16_32768)) :
         (floorZ - ceilZ >= ZOFFSET4))
     return 0;
 
@@ -648,10 +648,10 @@ static int32_t A_GetWaterZOffset(int spritenum);
 
 GAMEEXEC_STATIC void VM_Move(void)
 {
-    // NOTE: commented out condition is dead since r3159 (making hi/lotag unsigned).
-    // XXX: Does it break anything? Where are movflags with all bits set created?
-    const uint16_t * const movflagsptr = &AC_MOVFLAGS(vm.pSprite, &actor[vm.spriteNum]);
-    int const movflags = /*(*movflagsptr==-1) ? 0 :*/ *movflagsptr;
+    auto const movflagsptr = &AC_MOVFLAGS(vm.pSprite, &actor[vm.spriteNum]);
+    // NOTE: test against -1 commented out and later revived in source history
+    // XXX: Does its presence/absence break anything? Where are movflags with all bits set created?
+    int const movflags = (*movflagsptr == (std::remove_pointer<decltype(movflagsptr)>::type)-1) ? 0 : *movflagsptr;
     int const deadflag = (A_CheckEnemySprite(vm.pSprite) && vm.pSprite->extra <= 0);
 
     AC_COUNT(vm.pData)++;
@@ -3692,7 +3692,7 @@ nullquote:
 
                 if (foundSect >= 0 && isanearoperator(sector[foundSect].lotag))
                     if ((sector[foundSect].lotag&0xff) == ST_23_SWINGING_DOOR || sector[foundSect].floorz == sector[foundSect].ceilingz)
-                        if ((sector[foundSect].lotag&(16384|32768)) == 0)
+                        if ((sector[foundSect].lotag&(int16_t)(16384|INT16_32768)) == 0)
                         {
                             int32_t j;
 
@@ -5536,8 +5536,8 @@ finish_qsprintf:
                         G_OperateRespawns(vm.pSprite->yvel);
                     break;
                 default:
-                    //                if (vm.pSprite->hitag >= 0)
-                    G_OperateRespawns(vm.pSprite->hitag);
+                    if (vm.pSprite->hitag >= 0)
+                        G_OperateRespawns(vm.pSprite->hitag);
                     break;
             }
             continue;
@@ -5642,7 +5642,7 @@ void VM_UpdateAnim(int spriteNum, int32_t *pData)
         int const action_incval = actor[spriteNum].ac.incval;
         int const action_delay  = actor[spriteNum].ac.delay;
 #endif
-        uint16_t *actionticsptr = &AC_ACTIONTICS(&sprite[spriteNum], &actor[spriteNum]);
+        auto actionticsptr = &AC_ACTIONTICS(&sprite[spriteNum], &actor[spriteNum]);
         *actionticsptr += TICSPERFRAME;
 
         if (*actionticsptr > action_delay)
diff --git a/source/duke3d/src/gamestructures.cpp b/source/duke3d/src/gamestructures.cpp
index 9e1fd7c41..eeb06edc2 100644
--- a/source/duke3d/src/gamestructures.cpp
+++ b/source/duke3d/src/gamestructures.cpp
@@ -856,8 +856,8 @@ int32_t __fastcall VM_GetWall(int32_t const wallNum, int32_t labelNum)
         case WALL_YPANNING: labelNum = pWall->ypanning; break;
         case WALL_LOTAG: labelNum = (int16_t)pWall->lotag; break;
         case WALL_HITAG: labelNum = (int16_t)pWall->hitag; break;
-        case WALL_ULOTAG: labelNum = pWall->lotag; break;
-        case WALL_UHITAG: labelNum = pWall->hitag; break;
+        case WALL_ULOTAG: labelNum = (uint16_t)pWall->lotag; break;
+        case WALL_UHITAG: labelNum = (uint16_t)pWall->hitag; break;
         case WALL_EXTRA: labelNum = pWall->extra; break;
         case WALL_BLEND:
 #ifdef NEW_MAP_FORMAT
@@ -900,8 +900,8 @@ void __fastcall VM_SetWall(int32_t const wallNum, int32_t const labelNum, int32_
         case WALL_YPANNING: pWall->ypanning = iSet; break;
         case WALL_LOTAG: pWall->lotag = (int16_t)iSet; break;
         case WALL_HITAG: pWall->hitag = (int16_t)iSet; break;
-        case WALL_ULOTAG: pWall->lotag = iSet; break;
-        case WALL_UHITAG: pWall->hitag = iSet; break;
+        case WALL_ULOTAG: pWall->lotag = (uint16_t)iSet; break;
+        case WALL_UHITAG: pWall->hitag = (uint16_t)iSet; break;
         case WALL_EXTRA: pWall->extra = iSet; break;
         case WALL_BLEND:
 #ifdef NEW_MAP_FORMAT
@@ -956,8 +956,8 @@ int32_t __fastcall VM_GetSector(int32_t const sectNum, int32_t labelNum)
         case SECTOR_FOGPAL: labelNum = pSector->fogpal; break;
         case SECTOR_LOTAG: labelNum = (int16_t)pSector->lotag; break;
         case SECTOR_HITAG: labelNum = (int16_t)pSector->hitag; break;
-        case SECTOR_ULOTAG: labelNum = pSector->lotag; break;
-        case SECTOR_UHITAG: labelNum = pSector->hitag; break;
+        case SECTOR_ULOTAG: labelNum = (uint16_t)pSector->lotag; break;
+        case SECTOR_UHITAG: labelNum = (uint16_t)pSector->hitag; break;
         case SECTOR_EXTRA: labelNum = pSector->extra; break;
         case SECTOR_CEILINGBUNCH:
         case SECTOR_FLOORBUNCH:
@@ -1020,8 +1020,8 @@ void __fastcall VM_SetSector(int32_t const sectNum, int32_t const labelNum, int3
         case SECTOR_FOGPAL: pSector->fogpal = iSet; break;
         case SECTOR_LOTAG: pSector->lotag = (int16_t) iSet; break;
         case SECTOR_HITAG: pSector->hitag = (int16_t) iSet; break;
-        case SECTOR_ULOTAG: pSector->lotag = iSet; break;
-        case SECTOR_UHITAG: pSector->hitag = iSet; break;
+        case SECTOR_ULOTAG: pSector->lotag = (uint16_t)iSet; break;
+        case SECTOR_UHITAG: pSector->hitag = (uint16_t)iSet; break;
         case SECTOR_EXTRA: pSector->extra = iSet; break;
         case SECTOR_CEILINGBUNCH:
         case SECTOR_FLOORBUNCH:
@@ -1064,8 +1064,8 @@ void __fastcall VM_SetSprite(int32_t const spriteNum, int32_t const labelNum, in
         case ACTOR_ZVEL: pSprite->zvel = iSet; break;
         case ACTOR_LOTAG: pSprite->lotag = (int16_t)iSet; break;
         case ACTOR_HITAG: pSprite->hitag = (int16_t)iSet; break;
-        case ACTOR_ULOTAG: pSprite->lotag = iSet; break;
-        case ACTOR_UHITAG: pSprite->hitag = iSet; break;
+        case ACTOR_ULOTAG: pSprite->lotag = (uint16_t)iSet; break;
+        case ACTOR_UHITAG: pSprite->hitag = (uint16_t)iSet; break;
         case ACTOR_EXTRA: pSprite->extra = iSet; break;
         case ACTOR_HTCGG: actor[spriteNum].cgg = iSet; break;
         case ACTOR_HTPICNUM: actor[spriteNum].picnum = iSet; break;
@@ -1136,8 +1136,8 @@ int32_t __fastcall VM_GetSprite(int32_t const spriteNum, int32_t labelNum, int32
         case ACTOR_ZVEL: labelNum = pSprite->zvel; break;
         case ACTOR_LOTAG: labelNum = (int16_t)pSprite->lotag; break;
         case ACTOR_HITAG: labelNum = (int16_t)pSprite->hitag; break;
-        case ACTOR_ULOTAG: labelNum = pSprite->lotag; break;
-        case ACTOR_UHITAG: labelNum = pSprite->hitag; break;
+        case ACTOR_ULOTAG: labelNum = (uint16_t)pSprite->lotag; break;
+        case ACTOR_UHITAG: labelNum = (uint16_t)pSprite->hitag; break;
         case ACTOR_EXTRA: labelNum = pSprite->extra; break;
         case ACTOR_HTCGG: labelNum = actor[spriteNum].cgg; break;
         case ACTOR_HTPICNUM: labelNum = actor[spriteNum].picnum; break;
@@ -1213,8 +1213,8 @@ error:
         case ACTOR_ZVEL: labelNum = tspr->zvel; break;
         case ACTOR_LOTAG: labelNum = (int16_t) tspr->lotag; break;
         case ACTOR_HITAG: labelNum = (int16_t) tspr->hitag; break;
-        case ACTOR_ULOTAG: labelNum = tspr->lotag; break;
-        case ACTOR_UHITAG: labelNum = tspr->hitag; break;
+        case ACTOR_ULOTAG: labelNum = (uint16_t)tspr->lotag; break;
+        case ACTOR_UHITAG: labelNum = (uint16_t)tspr->hitag; break;
         case ACTOR_EXTRA: labelNum = tspr->extra; break;
         default: labelNum = -1; break;
     }
@@ -1260,8 +1260,8 @@ error:
         case ACTOR_ZVEL: tspr->zvel = iSet; break;
         case ACTOR_LOTAG: tspr->lotag = (int16_t) iSet; break;
         case ACTOR_HITAG: tspr->hitag = (int16_t) iSet; break;
-        case ACTOR_ULOTAG: tspr->lotag = iSet; break;
-        case ACTOR_UHITAG: tspr->hitag = iSet; break;
+        case ACTOR_ULOTAG: tspr->lotag = (uint16_t)iSet; break;
+        case ACTOR_UHITAG: tspr->hitag = (uint16_t)iSet; break;
         case ACTOR_EXTRA: tspr->extra = iSet; break;
     }
 }
diff --git a/source/duke3d/src/premap.cpp b/source/duke3d/src/premap.cpp
index b1579fc9e..1887680ed 100644
--- a/source/duke3d/src/premap.cpp
+++ b/source/duke3d/src/premap.cpp
@@ -1012,7 +1012,7 @@ static void G_SetupRotfixedSprites(void)
     }
 }
 
-static inline int G_CheckExitSprite(int spriteNum) { return (sprite[spriteNum].lotag == UINT16_MAX && (sprite[spriteNum].cstat & 16)); }
+static inline int G_CheckExitSprite(int spriteNum) { return ((uint16_t)sprite[spriteNum].lotag == UINT16_MAX && (sprite[spriteNum].cstat & 16)); }
 
 static void prelevel(char g)
 {
@@ -1040,7 +1040,7 @@ static void prelevel(char g)
         case ST_20_CEILING_DOOR:
         case ST_22_SPLITTING_DOOR:
             if (sector[i].floorz > sector[i].ceilingz)
-                sector[i].lotag |= 32768;
+                sector[i].lotag |= INT16_32768;
             continue;
         }
 
@@ -1071,7 +1071,7 @@ static void prelevel(char g)
             continue;
         }
 
-        if (sector[i].lotag == UINT16_MAX)
+        if ((uint16_t)sector[i].lotag == UINT16_MAX)
         {
             g_player[0].ps->exitx = wall[sector[i].wallptr].x;
             g_player[0].ps->exity = wall[sector[i].wallptr].y;
diff --git a/source/duke3d/src/sector.cpp b/source/duke3d/src/sector.cpp
index 9c6046863..39619da27 100644
--- a/source/duke3d/src/sector.cpp
+++ b/source/duke3d/src/sector.cpp
@@ -818,7 +818,7 @@ REDODOOR:
             if (j >= 0) j = sector[j].ceilingz;
             else
             {
-                pSector->lotag |= 32768;
+                pSector->lotag |= INT16_32768;
                 goto REDODOOR;
             }
         }
@@ -1183,8 +1183,10 @@ int P_ActivateSwitch(int playerNum, int wallOrSprite, int switchType)
     if (wallOrSprite < 0)
         return 0;
 
-    int lotag, hitag, nSwitchPicnum, nSwitchPal;
     vec3_t davector;
+    int16_t lotag, hitag;
+    int16_t nSwitchPicnum;
+    uint8_t nSwitchPal;
 
     if (switchType == SWITCH_SPRITE) // A wall sprite
     {
@@ -1370,7 +1372,7 @@ int P_ActivateSwitch(int playerNum, int wallOrSprite, int switchType)
         }
     }
 
-    if (lotag == UINT16_MAX)
+    if ((uint16_t)lotag == UINT16_MAX)
     {
         P_EndLevel();
         return 1;
@@ -2880,7 +2882,7 @@ void P_CheckSectors(int playerNum)
     if (pPlayer->cursectnum > -1)
     {
         sectortype *const pSector = &sector[pPlayer->cursectnum];
-        switch (pSector->lotag)
+        switch ((uint16_t)pSector->lotag)
         {
             case 32767:
                 pSector->lotag = 0;