diff --git a/src/hardware/hw_main.c b/src/hardware/hw_main.c
index 6a664d39b..774ff8c1c 100644
--- a/src/hardware/hw_main.c
+++ b/src/hardware/hw_main.c
@@ -2690,6 +2690,8 @@ static void HWR_AddLine(seg_t * line)
 	// SoM: Backsector needs to be run through R_FakeFlat
 	static sector_t tempsec;
 
+	sector_t *thissec = R_PointInSubsector(viewx, viewy)->sector;
+
 	if (line->polyseg && !(line->polyseg->flags & POF_RENDERSIDES))
 		return;
 
@@ -2811,11 +2813,14 @@ static void HWR_AddLine(seg_t * line)
 		SLOPEPARAMS( gr_backsector->c_slope, backc1,  backc2,  gr_backsector->ceilingheight)
 #undef SLOPEPARAMS
 
-		// Closed door.
-		if ((backc1 <= frontf1 && backc2 <= frontf2)
-			|| (backf1 >= frontc1 && backf2 >= frontc2))
+		if (thissec != gr_backsector && thissec != gr_frontsector)
 		{
-			goto clipsolid;
+			// Closed door.
+			if ((backc1 <= frontf1 && backc2 <= frontf2)
+				|| (backf1 >= frontc1 && backf2 >= frontc2))
+			{
+				goto clipsolid;
+			}
 		}
 
 		// Window.
@@ -2828,10 +2833,13 @@ static void HWR_AddLine(seg_t * line)
 	else
 #endif
 	{
-		// Closed door.
-		if (gr_backsector->ceilingheight <= gr_frontsector->floorheight ||
-			gr_backsector->floorheight >= gr_frontsector->ceilingheight)
-			goto clipsolid;
+		if (thissec != gr_backsector && thissec != gr_frontsector)
+		{
+			// Closed door.
+			if (gr_backsector->ceilingheight <= gr_frontsector->floorheight ||
+				gr_backsector->floorheight >= gr_frontsector->ceilingheight)
+				goto clipsolid;
+		}
 
 		// Window.
 		if (gr_backsector->ceilingheight != gr_frontsector->ceilingheight ||