diff --git a/doc/fixes36.1 b/doc/fixes36.1
index 8237d8dbd..9c1b935d1 100644
--- a/doc/fixes36.1
+++ b/doc/fixes36.1
@@ -536,6 +536,7 @@ gas spore explosion killing a gas spore which triggers a recursive explosion
 	would have killer reason for outer call clobbered by inner one; when
 	they were both "gas spore's explosion" it wouldn't be noticeable (see
 	corresponding post-3.6.0 entry for more...)
+wizard mode 'sanity_check' gave spurious "mon not on map" warnings when mounted
 
 
 Fixes to Post-3.6.0 Problems that Were Exposed Via git Repository
diff --git a/src/mon.c b/src/mon.c
index 456e601e7..ae1493989 100644
--- a/src/mon.c
+++ b/src/mon.c
@@ -1,4 +1,4 @@
-/* NetHack 3.6	mon.c	$NHDT-Date: 1514769571 2018/01/01 01:19:31 $  $NHDT-Branch: NetHack-3.6.0 $:$NHDT-Revision: 1.246 $ */
+/* NetHack 3.6	mon.c	$NHDT-Date: 1522540516 2018/03/31 23:55:16 $  $NHDT-Branch: NetHack-3.6.0 $:$NHDT-Revision: 1.250 $ */
 /* Copyright (c) Stichting Mathematisch Centrum, Amsterdam, 1985. */
 /* NetHack may be freely redistributed.  See license for details. */
 
@@ -86,14 +86,21 @@ mon_sanity_check()
         if (DEADMONSTER(mtmp))
             continue;
         x = mtmp->mx, y = mtmp->my;
-        if (!isok(x, y) && !(mtmp->isgd && x == 0 && y == 0))
+        if (!isok(x, y) && !(mtmp->isgd && x == 0 && y == 0)) {
             impossible("mon (%s) claims to be at <%d,%d>?",
                        fmt_ptr((genericptr_t) mtmp), x, y);
-        else if (level.monsters[x][y] != mtmp)
+        } else if (mtmp == u.usteed) {
+            /* steed is in fmon list but not on the map; its
+               <mx,my> coordinates should match hero's location */
+            if (x != u.ux || y != u.uy)
+                impossible("steed (%s) claims to be at <%d,%d>?",
+                           fmt_ptr((genericptr_t) mtmp), x, y);
+        } else if (level.monsters[x][y] != mtmp) {
             impossible("mon (%s) at <%d,%d> is not there!",
                        fmt_ptr((genericptr_t) mtmp), x, y);
-        else if (mtmp->wormno)
+        } else if (mtmp->wormno) {
             sanity_check_worm(mtmp);
+        }
     }
 
     for (x = 0; x < COLNO; x++)
@@ -105,6 +112,9 @@ mon_sanity_check()
                 if (!m)
                     impossible("map mon (%s) at <%d,%d> not in fmon list!",
                                fmt_ptr((genericptr_t) mtmp), x, y);
+                else if (mtmp == u.usteed)
+                    impossible("steed (%s) is on the map at <%d,%d>!",
+                               fmt_ptr((genericptr_t) mtmp), x, y);
                 else if ((mtmp->mx != x || mtmp->my != y)
                          && mtmp->data != &mons[PM_LONG_WORM])
                     impossible("map mon (%s) at <%d,%d> is found at <%d,%d>?",