diff --git a/src/objects/random-item.c b/src/objects/random-item.c
index 9abb7cb93..4ec2106fe 100644
--- a/src/objects/random-item.c
+++ b/src/objects/random-item.c
@@ -139,7 +139,7 @@ boolean Obj_RandomItemSpawnIn(mobj_t *mobj)
 fixed_t Obj_RandomItemScale(fixed_t oldScale)
 {
 	const fixed_t intendedScale = oldScale * 3;
-	const fixed_t maxScale = FixedDiv(128*FRACUNIT, mobjinfo[MT_RANDOMITEM].radius); // don't make them larger than the blockmap can handle
+	const fixed_t maxScale = FixedDiv(MAPBLOCKSIZE, mobjinfo[MT_RANDOMITEM].radius); // don't make them larger than the blockmap can handle
 
 	return min(intendedScale, maxScale);
 }
diff --git a/src/p_local.h b/src/p_local.h
index ddb01d565..44655cc70 100644
--- a/src/p_local.h
+++ b/src/p_local.h
@@ -50,9 +50,7 @@ extern "C" {
 #define BMBOUNDFIX(xl, xh, yl, yh) {if (xl > xh) xl = 0; if (yl > yh) yl = 0;}
 
 // MAXRADIUS is for precalculated sector block boxes
-// the spider demon is larger,
-// but we do not have any moving sectors nearby
-#define MAXRADIUS (32*FRACUNIT)
+#define MAXRADIUS (MAPBLOCKSIZE >> 1)
 
 // max Z move up or down without jumping
 // above this, a height difference is considered as a 'dropoff'
diff --git a/src/p_mobj.c b/src/p_mobj.c
index 82135b18a..cb942be7f 100644
--- a/src/p_mobj.c
+++ b/src/p_mobj.c
@@ -13139,7 +13139,7 @@ static boolean P_SetupSpawnedMapThing(mapthing_t *mthing, mobj_t *mobj, boolean
 		// Ambush = double size (grounded) / half size (aerial)
 		if (!(mthing->args[2] & TMICF_INVERTSIZE) == !P_IsObjectOnGround(mobj))
 		{
-			mobj->extravalue1 = min(mobj->extravalue1 << 1, FixedDiv(128*FRACUNIT, mobj->info->radius)); // don't make them larger than the blockmap can handle
+			mobj->extravalue1 = min(mobj->extravalue1 << 1, FixedDiv(MAPBLOCKSIZE, mobj->info->radius)); // don't make them larger than the blockmap can handle
 			mobj->scalespeed <<= 1;
 		}
 		break;