diff --git a/src/r_plane.cpp b/src/r_plane.cpp
index ea2678e96..394a77993 100644
--- a/src/r_plane.cpp
+++ b/src/r_plane.cpp
@@ -1294,6 +1294,7 @@ void R_DrawSkyBoxes ()
 		ds_p->sprtopclip = R_NewOpening (pl->maxx - pl->minx + 1);
 		ds_p->maskedtexturecol = ds_p->swall = -1;
 		ds_p->bFogBoundary = false;
+		ds_p->curline = NULL;
 		memcpy (openings + ds_p->sprbottomclip, floorclip + pl->minx, (pl->maxx - pl->minx + 1)*sizeof(short));
 		memcpy (openings + ds_p->sprtopclip, ceilingclip + pl->minx, (pl->maxx - pl->minx + 1)*sizeof(short));
 
diff --git a/src/r_things.cpp b/src/r_things.cpp
index cbcfbc295..3a6773c70 100644
--- a/src/r_things.cpp
+++ b/src/r_things.cpp
@@ -322,11 +322,8 @@ nextpost:
 //
 bool R_ClipSpriteColumnWithPortals (fixed_t x, fixed_t y, vissprite_t* spr)
 {
-	size_t numdrawsegs = ds_p-firstdrawseg;
-	for (int i = (int)numdrawsegs-1; i >= 0; i--)
+	for (drawseg_t* seg = ds_p; seg-- > firstdrawseg; ) // copied code from killough below
 	{
-		drawseg_t* seg = &firstdrawseg[i];
-
 		// ignore segs from other portals
 		if (seg->CurrentPortalUniq != CurrentPortalUniq)
 			continue;