diff --git a/include/extern.h b/include/extern.h
index 0d7dfdedb..1d35b8bb5 100644
--- a/include/extern.h
+++ b/include/extern.h
@@ -1282,6 +1282,7 @@ E struct permonst *NDECL(courtmon);
 E void FDECL(save_rooms, (int));
 E void FDECL(rest_rooms, (int));
 E struct mkroom *FDECL(search_special, (SCHAR_P));
+E int FDECL(cmap_to_type, (int));
 
 /* ### mon.c ### */
 
diff --git a/src/display.c b/src/display.c
index 68143db75..b48d06833 100644
--- a/src/display.c
+++ b/src/display.c
@@ -414,9 +414,16 @@ display_monster(x, y, mon, sightflags, worm_tail)
 		 * mappearance is currently set to an S_ index value in
 		 * makemon.c.
 		 */
-		register int glyph = cmap_to_glyph(mon->mappearance);
+		int sym = mon->mappearance, glyph = cmap_to_glyph(sym);
+
 		levl[x][y].glyph = glyph;
-		if (!sensed) show_glyph(x,y, glyph);
+		if (!sensed) {
+		    show_glyph(x,y, glyph);
+#ifdef DUNGEON_OVERVIEW
+		    /* override real topology with mimic's fake one */
+		    lastseentyp[x][y] = cmap_to_type(sym);
+#endif
+		}
 		break;
 	    }
 
diff --git a/src/dungeon.c b/src/dungeon.c
index 98dc0e72f..c0907695b 100644
--- a/src/dungeon.c
+++ b/src/dungeon.c
@@ -5,9 +5,6 @@
 #include "hack.h"
 #include "dgn_file.h"
 #include "dlb.h"
-#ifdef DUNGEON_OVERVIEW
-#include "display.h"
-#endif /* DUNGEON_OVERVIEW */
 
 #define DUNGEON_FILE	"dungeon"
 
@@ -2132,7 +2129,7 @@ recalc_mapseen()
 		}
 	}
 
-	/* Update styp with typ if and only if it is in sight or the hero can
+	/* Update lastseentyp with typ if and only if it is in sight or the hero can
 	 * feel it on their current location (i.e. not levitating).  This *should*
 	 * give the "last known typ" for each dungeon location.  (At the very least,
 	 * it's a better assumption than determining what the player knows from
@@ -2147,17 +2144,20 @@ recalc_mapseen()
 	 * Although no current windowing systems (can) do this, this would add the
 	 * ability to have non-dungeon glyphs float above the last known dungeon
 	 * glyph (i.e. items on fountains).
-	 *
-	 * (vision-related styp update done in loop below)
 	 */
 	if (!Levitation)
 		lastseentyp[u.ux][u.uy] = levl[u.ux][u.uy].typ;
 
 	for (x = 0; x < COLNO; x++) {
 		for (y = 0; y < ROWNO; y++) {
-			/* update styp from viz_array */
-			if (viz_array[y][x] & IN_SIGHT)
-				lastseentyp[x][y] = levl[x][y].typ;
+			if (cansee(x, y)) {
+			    struct monst *mtmp = m_at(x, y);
+
+			    lastseentyp[x][y] =
+	    (mtmp && mtmp->m_ap_type == M_AP_FURNITURE && canseemon(mtmp)) ?
+					cmap_to_type(mtmp->mappearance) :
+					levl[x][y].typ;
+			}
 
 			switch (lastseentyp[x][y]) {
 			/*
diff --git a/src/mkroom.c b/src/mkroom.c
index fc7607037..67be40e27 100644
--- a/src/mkroom.c
+++ b/src/mkroom.c
@@ -12,6 +12,7 @@
  *	courtmon() -- generate a court monster
  *	save_rooms() -- save rooms into file fd
  *	rest_rooms() -- restore rooms from file fd
+ *	cmap_to_type() -- convert S_xxx symbol to XXX topology code
  */
 
 #include "hack.h"
@@ -783,4 +784,59 @@ int	fd;
 	subrooms[nsubroom].hx = -1;
 }
 
+/* convert a display symbol for terrain into topology type;
+   used for remembered terrain when mimics pose as furniture */
+int
+cmap_to_type(sym)
+int sym;
+{
+    int typ = STONE;	/* catchall */
+
+    switch (sym) {
+    case S_stone:	typ = STONE; break;
+    case S_vwall:	typ = VWALL; break;
+    case S_hwall:	typ = HWALL; break;
+    case S_tlcorn:	typ = TLCORNER; break;
+    case S_trcorn:	typ = TRCORNER; break;
+    case S_blcorn:	typ = BLCORNER; break;
+    case S_brcorn:	typ = BRCORNER; break;
+    case S_crwall:	typ = CROSSWALL; break;
+    case S_tuwall:	typ = TUWALL; break;
+    case S_tdwall:	typ = TDWALL; break;
+    case S_tlwall:	typ = TLWALL; break;
+    case S_trwall:	typ = TRWALL; break;
+    case S_ndoor:		/* no door (empty doorway) */
+    case S_vodoor:		/* open door in vertical wall */
+    case S_hodoor:		/* open door in horizontal wall */
+    case S_vcdoor:		/* closed door in vertical wall */
+    case S_hcdoor:	typ = DOOR; break;
+    case S_bars:	typ = IRONBARS; break;
+    case S_tree:	typ = TREE; break;
+    case S_room:	typ = ROOM; break;
+    case S_corr:
+    case S_litcorr:	typ = CORR; break;
+    case S_upstair:
+    case S_dnstair:	typ = STAIRS; break;
+    case S_upladder:
+    case S_dnladder:	typ = LADDER; break;
+    case S_altar:	typ = ALTAR; break;
+    case S_grave:	typ = GRAVE; break;
+    case S_throne:	typ = THRONE; break;
+    case S_sink:	typ = SINK; break;
+    case S_fountain:	typ = FOUNTAIN; break;
+    case S_pool:	typ = POOL; break;
+    case S_ice:		typ = ICE; break;
+    case S_lava:	typ = LAVAPOOL; break;
+    case S_vodbridge:		/* open drawbridge spanning north/south */
+    case S_hodbridge:	typ = DRAWBRIDGE_DOWN; break; /* east/west */
+    case S_vcdbridge:		/* closed drawbridge in vertical wall */
+    case S_hcdbridge:	typ = DBWALL; break;
+    case S_air:		typ = AIR; break;
+    case S_cloud:	typ = CLOUD; break;
+    case S_water:	typ = WATER; break;
+    default: break;	/* not a cmap symbol? */
+    }
+    return typ;
+}
+
 /*mkroom.c*/