diff --git a/doc/fixes36.1 b/doc/fixes36.1
index f2c33c3c3..80e792766 100644
--- a/doc/fixes36.1
+++ b/doc/fixes36.1
@@ -552,6 +552,9 @@ fix mention_walls reporting secret doors as solid stone
 jumping over water unintentionally moved hero through that water, causing
 	drowning if not able to water walk or fly
 try again to fix achievement recording bug with mines and sokoban prizes
+the fix for secret doors on special levels always having vertical orientation
+	resulted in some--but not all--secret doors within vertical walls
+	being displayed as horizontal walls while still hidden
 
 
 Platform- and/or Interface-Specific Fixes
diff --git a/src/sp_lev.c b/src/sp_lev.c
index f5a532230..5981a1b5e 100644
--- a/src/sp_lev.c
+++ b/src/sp_lev.c
@@ -1,4 +1,4 @@
-/* NetHack 3.6	sp_lev.c	$NHDT-Date: 1508879840 2017/10/24 21:17:20 $  $NHDT-Branch: NetHack-3.6.0 $:$NHDT-Revision: 1.90 $ */
+/* NetHack 3.6	sp_lev.c	$NHDT-Date: 1513879435 2017/12/21 18:03:55 $  $NHDT-Branch: NetHack-3.6.0 $:$NHDT-Revision: 1.93 $ */
 /*      Copyright (c) 1989 by Jean-Christophe Collet */
 /* NetHack may be freely redistributed.  See license for details. */
 
@@ -4181,8 +4181,8 @@ int dx, dy;
 genericptr_t arg;
 {
     xchar typ = *(xchar *) arg;
-    xchar x = dx;
-    xchar y = dy;
+    xchar x = dx, y = dy;
+    boolean left_or_right, up_and_down;
 
     if (!IS_DOOR(levl[x][y].typ) && levl[x][y].typ != SDOOR)
         levl[x][y].typ = (typ & D_SECRET) ? SDOOR : DOOR;
@@ -4192,12 +4192,35 @@ genericptr_t arg;
             typ = D_CLOSED;
     }
 
-    if (((isok(x-1,y) && IS_DOORJOIN(levl[x-1][y].typ)) || !isok(x-1,y))
-        || (isok(x+1,y) && IS_DOORJOIN(levl[x+1][y].typ)) || !isok(x+1,y))
-        levl[x][y].horizontal = 1;
-    else
-        levl[x][y].horizontal = 0;
-
+    /* If there's a wall or door on either the left side or right
+     * side (or both) of this secret door, make it be horizontal.
+     *
+     * It is feasible to put SDOOR in a corner, tee, or crosswall
+     * position, although once the door is found and opened it won't
+     * make a lot sense (diagonal access required).  Still, we try to
+     * handle that as best as possible.  For top or bottom tee, using
+     * horizontal is the best we can do.  For corner or crosswall,
+     * either horizontal or vertical are just as good as each other;
+     * we produce horizontal for corners and vertical for crosswalls.
+     * For left or right tee, using vertical is best.
+     *
+     * A secret door with no adjacent walls is also feasible and makes
+     * even less sense.  It will be displayed as a vertical wall while
+     * hidden and become a vertical door when found.
+     */
+    left_or_right = ((isok(x - 1, y) && (IS_WALL(levl[x - 1][y].typ)
+                                         || IS_DOOR(levl[x - 1][y].typ)
+                                         || levl[x - 1][y].typ == SDOOR))
+                     || (isok(x + 1, y) && (IS_WALL(levl[x + 1][y].typ)
+                                            || IS_DOOR(levl[x + 1][y].typ)
+                                            || levl[x + 1][y].typ == SDOOR)));
+    up_and_down = ((isok(x, y - 1) && (IS_WALL(levl[x][y - 1].typ)
+                                       || IS_DOOR(levl[x][y - 1].typ)
+                                       || levl[x][y - 1].typ == SDOOR))
+                   && (isok(x, y + 1) && (IS_WALL(levl[x][y + 1].typ)
+                                          || IS_DOOR(levl[x][y + 1].typ)
+                                          || levl[x][y + 1].typ == SDOOR)));
+    levl[x][y].horizontal = (left_or_right && !up_and_down) ? 1 : 0;
     levl[x][y].doormask = typ;
     SpLev_Map[x][y] = 1;
 }