diff --git a/src/p_local.h b/src/p_local.h
index 2f0b0626..926a5178 100644
--- a/src/p_local.h
+++ b/src/p_local.h
@@ -38,6 +38,9 @@
 #define MAPBMASK      (MAPBLOCKSIZE-1)
 #define MAPBTOFRAC    (MAPBLOCKSHIFT-FRACBITS)
 
+// Convenience macro to fix issue with collision along bottom/left edges of blockmap -Red
+#define BMBOUNDFIX(xl, xh, yl, yh) {if (xl > xh) xl = 0; if (yl > yh) yl = 0;}
+
 // player radius used only in am_map.c
 #define PLAYERRADIUS (16*FRACUNIT)
 
diff --git a/src/p_map.c b/src/p_map.c
index 5706e6d3..c88b91e9 100644
--- a/src/p_map.c
+++ b/src/p_map.c
@@ -1299,6 +1299,8 @@ boolean P_CheckPosition(mobj_t *thing, fixed_t x, fixed_t y)
 	yl = (unsigned)(tmbbox[BOXBOTTOM] - bmaporgy - MAXRADIUS)>>MAPBLOCKSHIFT;
 	yh = (unsigned)(tmbbox[BOXTOP] - bmaporgy + MAXRADIUS)>>MAPBLOCKSHIFT;
 
+	BMBOUNDFIX(xl, xh, yl, yh);
+
 #ifdef POLYOBJECTS
 	// Check polyobjects and see if tmfloorz/tmceilingz need to be altered
 	{
@@ -1516,6 +1518,8 @@ boolean P_CheckCameraPosition(fixed_t x, fixed_t y, camera_t *thiscam)
 	yl = (unsigned)(tmbbox[BOXBOTTOM] - bmaporgy)>>MAPBLOCKSHIFT;
 	yh = (unsigned)(tmbbox[BOXTOP] - bmaporgy)>>MAPBLOCKSHIFT;
 
+	BMBOUNDFIX(xl, xh, yl, yh);
+
 #ifdef POLYOBJECTS
 	// Check polyobjects and see if tmfloorz/tmceilingz need to be altered
 	{
@@ -1943,6 +1947,8 @@ boolean P_TryMove(mobj_t *thing, fixed_t x, fixed_t y, boolean allowdropoff)
 		xh = (unsigned)(thing->x + MAXRADIUS - bmaporgx)>>MAPBLOCKSHIFT;
 		xl = (unsigned)(thing->x - MAXRADIUS - bmaporgx)>>MAPBLOCKSHIFT;
 
+		BMBOUNDFIX(xl, xh, yl, yh);
+
 		stand = thing;
 		standx = x;
 		standy = y;
@@ -3029,6 +3035,8 @@ void P_RadiusAttack(mobj_t *spot, mobj_t *source, fixed_t damagedist)
 	xh = (unsigned)(spot->x + dist - bmaporgx)>>MAPBLOCKSHIFT;
 	xl = (unsigned)(spot->x - dist - bmaporgx)>>MAPBLOCKSHIFT;
 
+	BMBOUNDFIX(xl, xh, yl, yh);
+
 	bombspot = spot;
 	bombsource = source;
 	bombdamage = FixedMul(damagedist, spot->scale);
@@ -3650,6 +3658,8 @@ void P_CreateSecNodeList(mobj_t *thing, fixed_t x, fixed_t y)
 	yl = (unsigned)(tmbbox[BOXBOTTOM] - bmaporgy)>>MAPBLOCKSHIFT;
 	yh = (unsigned)(tmbbox[BOXTOP] - bmaporgy)>>MAPBLOCKSHIFT;
 
+	BMBOUNDFIX(xl, xh, yl, yh);
+
 	for (bx = xl; bx <= xh; bx++)
 		for (by = yl; by <= yh; by++)
 			P_BlockLinesIterator(bx, by, PIT_GetSectors);
@@ -3727,6 +3737,8 @@ void P_CreatePrecipSecNodeList(precipmobj_t *thing,fixed_t x,fixed_t y)
 	yl = (unsigned)(preciptmbbox[BOXBOTTOM] - bmaporgy)>>MAPBLOCKSHIFT;
 	yh = (unsigned)(preciptmbbox[BOXTOP] - bmaporgy)>>MAPBLOCKSHIFT;
 
+	BMBOUNDFIX(xl, xh, yl, yh);
+
 	for (bx = xl; bx <= xh; bx++)
 		for (by = yl; by <= yh; by++)
 			P_BlockLinesIterator(bx, by, PIT_GetPrecipSectors);
diff --git a/src/p_user.c b/src/p_user.c
index 6270d789..870f028c 100644
--- a/src/p_user.c
+++ b/src/p_user.c
@@ -2963,6 +2963,8 @@ static void P_DoTeeter(player_t *player)
 		xh = (unsigned)(player->mo->x + player->mo->radius - bmaporgx)>>MAPBLOCKSHIFT;
 		xl = (unsigned)(player->mo->x - player->mo->radius - bmaporgx)>>MAPBLOCKSHIFT;
 
+		BMBOUNDFIX(xl, xh, yl, yh);
+
 	// Polyobjects
 #ifdef POLYOBJECTS
 		validcount++;
@@ -8099,6 +8101,8 @@ boolean P_MoveChaseCamera(player_t *player, camera_t *thiscam, boolean resetcall
 		yl = (unsigned)(tmbbox[BOXBOTTOM] - bmaporgy)>>MAPBLOCKSHIFT;
 		yh = (unsigned)(tmbbox[BOXTOP] - bmaporgy)>>MAPBLOCKSHIFT;
 
+		BMBOUNDFIX(xl, xh, yl, yh);
+
 		for (by = yl; by <= yh; by++)
 			for (bx = xl; bx <= xh; bx++)
 			{