diff --git a/src/dungeon.c b/src/dungeon.c
index 33843e95b..96b99591d 100644
--- a/src/dungeon.c
+++ b/src/dungeon.c
@@ -1,4 +1,4 @@
-/* NetHack 3.6	dungeon.c	$NHDT-Date: 1446955297 2015/11/08 04:01:37 $  $NHDT-Branch: master $:$NHDT-Revision: 1.68 $ */
+/* NetHack 3.6	dungeon.c	$NHDT-Date: 1448862377 2015/11/30 05:46:17 $  $NHDT-Branch: master $:$NHDT-Revision: 1.69 $ */
 /* Copyright (c) Stichting Mathematisch Centrum, Amsterdam, 1985. */
 /* NetHack may be freely redistributed.  See license for details. */
 
@@ -1979,6 +1979,7 @@ get_annotation(lev)
 d_level *lev;
 {
     mapseen *mptr;
+
     if ((mptr = find_mapseen(lev)))
         return mptr->custom;
     return NULL;
@@ -2405,7 +2406,10 @@ recalc_mapseen()
                     mptr->feat.ngrave = count;
                 break;
             case ALTAR:
-                atmp = Amask2msa(levl[x][y].altarmask);
+                atmp = (Is_astralevel(&u.uz)
+                        && (levl[x][y].seenv & SVALL) != SVALL)
+                         ? MSA_NONE
+                         : Amask2msa(levl[x][y].altarmask);
                 if (!mptr->feat.naltar)
                     mptr->feat.msalign = atmp;
                 else if (mptr->feat.msalign != atmp)
diff --git a/src/read.c b/src/read.c
index 37867ee58..6f9b39a0b 100644
--- a/src/read.c
+++ b/src/read.c
@@ -1,4 +1,4 @@
-/* NetHack 3.6	read.c	$NHDT-Date: 1447987787 2015/11/20 02:49:47 $  $NHDT-Branch: master $:$NHDT-Revision: 1.123 $ */
+/* NetHack 3.6	read.c	$NHDT-Date: 1448862378 2015/11/30 05:46:18 $  $NHDT-Branch: master $:$NHDT-Revision: 1.125 $ */
 /* Copyright (c) Stichting Mathematisch Centrum, Amsterdam, 1985. */
 /* NetHack may be freely redistributed.  See license for details. */
 
@@ -776,6 +776,8 @@ int howmuch;
                 levl[zx][zy].glyph = cmap_to_glyph(S_stone);
                 lastseentyp[zx][zy] = STONE;
             }
+    /* forget overview data for this level */
+    forget_mapseen(ledger_no(&u.uz));
 }
 
 /* Forget all traps on the level. */