diff --git a/src/r_segs.c b/src/r_segs.c
index f0c8bc093..246d7ad00 100644
--- a/src/r_segs.c
+++ b/src/r_segs.c
@@ -2818,12 +2818,23 @@ void R_StoreWallRange(INT32 start, INT32 stop)
 			ffloor[i].f_pos >>= 4;
 #ifdef ESLOPE
 			ffloor[i].f_pos_slope >>= 4;
-			ffloor[i].f_frac = (centeryfrac>>4) - FixedMul(ffloor[i].f_pos, rw_scale);
-			ffloor[i].f_step = ((centeryfrac>>4) - FixedMul(ffloor[i].f_pos_slope, ds_p->scale2) - ffloor[i].f_frac)/(range);
-#else
-			ffloor[i].f_step = FixedMul(-rw_scalestep, ffloor[i].f_pos);
-			ffloor[i].f_frac = (centeryfrac>>4) - FixedMul(ffloor[i].f_pos, rw_scale);
 #endif
+			if (linedef->special == 41) // Horizon lines extend FOFs in contact with them too.
+			{
+				ffloor[i].f_step = 0;
+				ffloor[i].f_frac = (centeryfrac>>4);
+				topfrac++; // Prevent 1px HOM
+			}
+			else
+			{
+#ifdef ESLOPE
+				ffloor[i].f_frac = (centeryfrac>>4) - FixedMul(ffloor[i].f_pos, rw_scale);
+				ffloor[i].f_step = ((centeryfrac>>4) - FixedMul(ffloor[i].f_pos_slope, ds_p->scale2) - ffloor[i].f_frac)/(range);
+#else
+				ffloor[i].f_step = FixedMul(-rw_scalestep, ffloor[i].f_pos);
+				ffloor[i].f_frac = (centeryfrac>>4) - FixedMul(ffloor[i].f_pos, rw_scale);
+#endif
+			}
 		}
 	}