diff --git a/src/hardware/hw_main.c b/src/hardware/hw_main.c
index 5f0c25a59a0116b93604985d8eb6f9e9ebd612c0..51c976973d6a0db7aaeeaaa7e055af3592497fce 100644
--- a/src/hardware/hw_main.c
+++ b/src/hardware/hw_main.c
@@ -1973,7 +1973,7 @@ static void HWR_StoreWallRange(double startfrac, double endfrac)
 	{
 		// Single sided line... Deal only with the middletexture (if one exists)
 		gr_midtexture = R_GetTextureNum(gr_sidedef->midtexture);
-		if (gr_midtexture && gr_linedef->special != 41) // Ignore horizon line for OGL
+		if (gr_midtexture && gr_linedef->special != HORIZONSPECIAL) // Ignore horizon line for OGL
 		{
 			{
 				fixed_t     texturevpeg;
diff --git a/src/p_map.c b/src/p_map.c
index 97bff8156977c2b55b2d3364fde4db5b2bb6e448..753ce9eb5f299f823740c928b34d9405e07a052f 100644
--- a/src/p_map.c
+++ b/src/p_map.c
@@ -3471,7 +3471,7 @@ isblocking:
 		}
 
 		// see about climbing on the wall
-		if (!(checkline->flags & ML_NOCLIMB))
+		if (!(checkline->flags & ML_NOCLIMB) && checkline->special != HORIZONSPECIAL)
 		{
 			boolean canclimb;
 			angle_t climbangle, climbline;
diff --git a/src/r_defs.h b/src/r_defs.h
index 4d41f4f706c491b985af8eee2ba0f5087a5cfd71..6d0b10b706d27897c7445c92766ad7a4f074f9e2 100644
--- a/src/r_defs.h
+++ b/src/r_defs.h
@@ -410,6 +410,8 @@ typedef enum
 	ST_NEGATIVE
 } slopetype_t;
 
+#define HORIZONSPECIAL 41
+
 typedef struct line_s
 {
 	// Vertices, from v1 to v2.
diff --git a/src/r_segs.c b/src/r_segs.c
index 6eb81ce7a4a64a78a3cda0765bd64149fc0eb280..ee62bfc739faf207ade72cda308433522621592a 100644
--- a/src/r_segs.c
+++ b/src/r_segs.c
@@ -2694,7 +2694,7 @@ void R_StoreWallRange(INT32 start, INT32 stop)
 	worldbottomslope >>= 4;
 #endif
 
-	if (linedef->special == 41) { // HORIZON LINES
+	if (linedef->special == HORIZONSPECIAL) { // HORIZON LINES
 		topstep = bottomstep = 0;
 		topfrac = bottomfrac = (centeryfrac>>4);
 		topfrac++; // Prevent 1px HOM
@@ -2825,7 +2825,7 @@ void R_StoreWallRange(INT32 start, INT32 stop)
 #ifdef ESLOPE
 			ffloor[i].f_pos_slope >>= 4;
 #endif
-			if (linedef->special == 41) // Horizon lines extend FOFs in contact with them too.
+			if (linedef->special == HORIZONSPECIAL) // Horizon lines extend FOFs in contact with them too.
 			{
 				ffloor[i].f_step = 0;
 				ffloor[i].f_frac = (centeryfrac>>4);