diff --git a/src/r_bsp.c b/src/r_bsp.c
index d547d860a..e79a1cee3 100644
--- a/src/r_bsp.c
+++ b/src/r_bsp.c
@@ -395,6 +395,7 @@ sector_t *R_FakeFlat(sector_t *sec, sector_t *tempsec, INT32 *floorlightlevel,
 boolean R_IsEmptyLine(seg_t *line, sector_t *front, sector_t *back)
 {
 	return (
+		!R_IsDebugLine(line) &&
 		!line->polyseg &&
 		back->ceilingpic == front->ceilingpic
 		&& back->floorpic == front->floorpic
@@ -422,6 +423,19 @@ boolean R_IsEmptyLine(seg_t *line, sector_t *front, sector_t *back)
 		|| Tag_Compare(&front->tags, &back->tags)));
 }
 
+boolean R_IsDebugLine(seg_t *line)
+{
+	if (line->linedef->special == 2001) // Ring Racers: Finish Line
+	{
+		if (cv_debugfinishline.value)
+		{
+			return true;
+		}
+	}
+
+	return false;
+}
+
 //
 // R_AddLine
 // Clips the given segment and adds any visible pieces to the line list.
@@ -518,6 +532,14 @@ static void R_AddLine(seg_t *line)
 	if (!backsector)
 		goto clipsolid;
 
+	// Finish line debug: make solid walls pitch black. This
+	// contrasts areas that are impossible to traverse next to
+	// finish lines.
+	if (cv_debugfinishline.value && (line->linedef->flags & (ML_IMPASSABLE|ML_BLOCKPLAYERS)))
+	{
+		goto clipsolid;
+	}
+
 	backsector = R_FakeFlat(backsector, &tempsec, NULL, NULL, true);
 
 	doorclosed = 0;
@@ -529,7 +551,8 @@ static void R_AddLine(seg_t *line)
 
 	if (bothceilingssky && bothfloorssky) // everything's sky? let's save us a bit of time then
 	{
-		if (!line->polyseg &&
+		if (!R_IsDebugLine(line) &&
+			!line->polyseg &&
 			!line->sidedef->midtexture
 			&& ((!frontsector->ffloors && !backsector->ffloors)
 				|| Tag_Compare(&frontsector->tags, &backsector->tags)))
diff --git a/src/r_bsp.h b/src/r_bsp.h
index 5a24ffe47..051253a5e 100644
--- a/src/r_bsp.h
+++ b/src/r_bsp.h
@@ -59,6 +59,7 @@ extern polyobj_t **po_ptrs; // temp ptr array to sort polyobject pointers
 sector_t *R_FakeFlat(sector_t *sec, sector_t *tempsec, INT32 *floorlightlevel,
 	INT32 *ceilinglightlevel, boolean back);
 boolean R_IsEmptyLine(seg_t *line, sector_t *front, sector_t *back);
+boolean R_IsDebugLine(seg_t *line);
 
 INT32 R_GetPlaneLight(sector_t *sector, fixed_t planeheight, boolean underside);
 void R_Prep3DFloors(sector_t *sector);
diff --git a/src/r_main.c b/src/r_main.c
index dcb8e3316..9d001fc88 100644
--- a/src/r_main.c
+++ b/src/r_main.c
@@ -182,6 +182,8 @@ consvar_t cv_renderstats = CVAR_INIT ("renderstats", "Off", 0, CV_OnOff, NULL);
 
 consvar_t cv_drawpickups = CVAR_INIT ("drawpickups", "Yes", CV_CHEAT, CV_YesNo, NULL);
 
+consvar_t cv_debugfinishline = CVAR_INIT ("debugfinishline", "Off", CV_CHEAT, CV_OnOff, NULL);
+
 void SplitScreen_OnChange(void)
 {
 	UINT8 i;
@@ -1676,6 +1678,8 @@ void R_RegisterEngineStuff(void)
 
 	CV_RegisterVar(&cv_drawpickups);
 
+	CV_RegisterVar(&cv_debugfinishline);
+
 	// debugging
 
 	CV_RegisterVar(&cv_debugrender_contrast);
diff --git a/src/r_main.h b/src/r_main.h
index 208d846a9..40103561a 100644
--- a/src/r_main.h
+++ b/src/r_main.h
@@ -122,6 +122,7 @@ extern consvar_t cv_fov[MAXSPLITSCREENPLAYERS];
 extern consvar_t cv_skybox;
 extern consvar_t cv_tailspickup;
 extern consvar_t cv_drawpickups;
+extern consvar_t cv_debugfinishline;
 
 // debugging
 
diff --git a/src/r_segs.c b/src/r_segs.c
index 21318e4ce..830a7529d 100644
--- a/src/r_segs.c
+++ b/src/r_segs.c
@@ -26,6 +26,10 @@
 #include "p_slopes.h"
 #include "console.h" // con_clipviewtop
 #include "taglist.h"
+#include "r_draw.h"
+
+#define HEIGHTBITS              12
+#define HEIGHTUNIT              (1<<HEIGHTBITS)
 
 // OPTIMIZE: closed two sided lines as single sided
 
@@ -169,6 +173,32 @@ void R_RenderMaskedSegRange(drawseg_t *ds, INT32 x1, INT32 x2)
 	// OPTIMIZE: get rid of LIGHTSEGSHIFT globally
 	curline = ds->curline;
 
+	if (R_IsDebugLine(curline))
+	{
+		const UINT8 thickness = 4;
+		const UINT8 pal = (leveltime % 70 < 35) ? 0x23 : 0x00;
+
+		const INT32 horizon = ((centeryfrac>>4) + 1 + HEIGHTUNIT - 1) >> HEIGHTBITS;
+		const INT32 y = max(0, min(horizon, vid.height - thickness));
+
+		UINT8 *p = &topleft[x1 + (y * vid.width)];
+
+		range = max(x2 - x1, 0) + 1;
+
+		for (i = 0; i < thickness; ++i)
+		{
+			memset(p, pal, range);
+			p += vid.width;
+		}
+
+		return;
+	}
+
+	if (ds->maskedtexturecol == NULL)
+	{
+		return;
+	}
+
 	frontsector = curline->frontsector;
 	backsector = curline->backsector;
 	texnum = R_GetTextureNum(curline->sidedef->midtexture);
@@ -1161,8 +1191,6 @@ static boolean R_FFloorCanClip(visffloor_t *pfloor)
 //  textures.
 // CALLED: CORE LOOPING ROUTINE.
 //
-#define HEIGHTBITS              12
-#define HEIGHTUNIT              (1<<HEIGHTBITS)
 
 
 //profile stuff ---------------------------------------------------------
diff --git a/src/r_things.c b/src/r_things.c
index 458eaac4e..74cf29de8 100644
--- a/src/r_things.c
+++ b/src/r_things.c
@@ -2899,7 +2899,7 @@ static void R_CreateDrawNodes(maskcount_t* mask, drawnode_t* head, boolean temps
 			}
 			ds->curline->polyseg->visplane = NULL;
 		}
-		if (ds->maskedtexturecol)
+		if (ds->maskedtexturecol || R_IsDebugLine(ds->curline))
 		{
 			entry = R_CreateDrawNode(head);
 			entry->seg = ds;
@@ -3698,11 +3698,10 @@ static void R_DrawMaskedList (drawnode_t* head)
 			R_DoneWithNode(r2);
 			r2 = next;
 		}
-		else if (r2->seg && r2->seg->maskedtexturecol != NULL)
+		else if (r2->seg)
 		{
 			next = r2->prev;
 			R_RenderMaskedSegRange(r2->seg, r2->seg->x1, r2->seg->x2);
-			r2->seg->maskedtexturecol = NULL;
 			R_DoneWithNode(r2);
 			r2 = next;
 		}