diff --git a/source/games/sw/src/copysect.cpp b/source/games/sw/src/copysect.cpp
index 564edabde..9d021659e 100644
--- a/source/games/sw/src/copysect.cpp
+++ b/source/games/sw/src/copysect.cpp
@@ -173,8 +173,8 @@ void CopySectorMatch(int match)
                         // move sprites from source to dest - use center offset
 
                         // get center of src and dest sect
-                        SectorMidPoint(src_sp->sectnum, &sx, &sy, &trash);
-                        SectorMidPoint(dest_sp->sectnum, &dx, &dy, &trash);
+                        SectorMidPoint(src_sp->sector(), &sx, &sy, &trash);
+                        SectorMidPoint(dest_sp->sector(), &dx, &dy, &trash);
 
                         // get offset
                         src_xoff = sx - sp->x;
diff --git a/source/games/sw/src/game.h b/source/games/sw/src/game.h
index 0d55bd815..d121d6daa 100644
--- a/source/games/sw/src/game.h
+++ b/source/games/sw/src/game.h
@@ -1805,7 +1805,7 @@ ANIMATOR NullAnimator;
 int Distance(int x1, int y1, int x2, int y2);
 
 int NewStateGroup(DSWActor* actor, STATEp SpriteGroup[]);
-void SectorMidPoint(short sectnum, int *xmid, int *ymid, int *zmid);
+void SectorMidPoint(sectortype* sectnum, int *xmid, int *ymid, int *zmid);
 USERp SpawnUser(DSWActor* actor, short id, STATEp state);
 
 short ActorFindTrack(DSWActor* actor, int8_t player_dir, int track_type, int *track_point_num, int *track_dir);
diff --git a/source/games/sw/src/sector.cpp b/source/games/sw/src/sector.cpp
index 576a6d1f7..21d626b9d 100644
--- a/source/games/sw/src/sector.cpp
+++ b/source/games/sw/src/sector.cpp
@@ -591,12 +591,11 @@ void SectorSetup(void)
     }
 }
 
-void SectorMidPoint(short sectnum, int *xmid, int *ymid, int *zmid)
+void SectorMidPoint(sectortype* sectp, int *xmid, int *ymid, int *zmid)
 {
-    auto sectp = &sector[sectnum];
     int xsum = 0, ysum = 0;
 
-    for(auto& wal : wallsofsector(sectnum))
+    for(auto& wal : wallsofsector(sectp))
     {
         xsum += wal.x;
         ysum += wal.y;
@@ -685,8 +684,8 @@ int SectorDistanceByMid(short sect1, int sect2)
 {
     int sx1, sy1, sx2, sy2, trash;
 
-    SectorMidPoint(sect1, &sx1, &sy1, &trash);
-    SectorMidPoint(sect2, &sx2, &sy2, &trash);
+    SectorMidPoint(&sector[sect1], &sx1, &sy1, &trash);
+    SectorMidPoint(&sector[sect2], &sx2, &sy2, &trash);
 
     // return the distance between the two sectors.
     return Distance(sx1, sy1, sx2, sy2);
@@ -880,7 +879,7 @@ void SectorExp(DSWActor* actor, short sectnum, short orig_ang, int zh)
     int x,y,z;
 
     RESET(sp->cstat, CSTAT_SPRITE_ALIGNMENT_WALL|CSTAT_SPRITE_ALIGNMENT_FLOOR);
-    SectorMidPoint(sectnum, &x, &y, &z);
+    SectorMidPoint(&sector[sectnum], &x, &y, &z);
     sp->ang = orig_ang;
     sp->x = x;
     sp->y = y;
diff --git a/source/games/sw/src/track.cpp b/source/games/sw/src/track.cpp
index 317f9fd56..d196be067 100644
--- a/source/games/sw/src/track.cpp
+++ b/source/games/sw/src/track.cpp
@@ -1091,7 +1091,7 @@ void SetupSectorObject(short sectnum, short tag)
     case TAG_OBJECT_CENTER - 500:
 
         sop->mid_sector = sectnum;
-        SectorMidPoint(sectnum, &sop->xmid, &sop->ymid, &sop->zmid);
+        SectorMidPoint(&sector[sectnum], &sop->xmid, &sop->ymid, &sop->zmid);
         //sop->zmid = sector[sectnum].floorz;
         //sop->zmid = DIV2(sector[sectnum].floorz + sector[sectnum].ceilingz);