diff --git a/include/align.h b/include/align.h
index f6539ceed..055fb13ed 100644
--- a/include/align.h
+++ b/include/align.h
@@ -1,4 +1,4 @@
-/* NetHack 3.7	align.h	$NHDT-Date: 1596498525 2020/08/03 23:48:45 $  $NHDT-Branch: NetHack-3.7 $:$NHDT-Revision: 1.11 $ */
+/* NetHack 3.7	align.h	$NHDT-Date: 1604105154 2020/10/31 00:45:54 $  $NHDT-Branch: NetHack-3.7 $:$NHDT-Revision: 1.14 $ */
 /* Copyright (c) Mike Stephenson, Izchak Miller  1991.		  */
 /* NetHack may be freely redistributed.  See license for details. */
 
@@ -30,27 +30,30 @@ typedef struct align { /* alignment & record */
 #define AM_LAWFUL 4
 
 #define AM_MASK 7
-/* Some altars are considered as shrines, so we need a flag. */
+/* Some altars are considered as shrines, so we need a flag for that
+   for the altarmask field of struct rm. */
 #define AM_SHRINE 8
 
-#define AM_SPLEV_CO 3
-#define AM_SPLEV_NONCO 7
+/* special level flags, gone by the time the level has been loaded */
+#define AM_SPLEV_CO     3 /* co-aligned: force alignment to match hero's  */
+#define AM_SPLEV_NONCO  7 /* non-co-aligned: force alignment to not match */
 #define AM_SPLEV_RANDOM 8
 
-#define Amask2align(x)                                          \
-    ((aligntyp)((!(x)) ? A_NONE : ((x) == AM_LAWFUL) ? A_LAWFUL \
-                                                     : ((int) x) - 2))
+#define Amask2align(x) \
+    ((aligntyp) ((((x) & AM_MASK) == 0) ? A_NONE                \
+                 : (((x) & AM_MASK) == AM_LAWFUL) ? A_LAWFUL    \
+                   : ((int) (x) - 2))) /* 2 => 0, 1 => -1 */
 #define Align2amask(x) \
-    (((x) == A_NONE) ? AM_NONE : ((x) == A_LAWFUL) ? AM_LAWFUL : (x) + 2)
+    ((unsigned) (((x) == A_NONE) ? AM_NONE                      \
+                 : ((x) == A_LAWFUL) ? AM_LAWFUL                \
+                   : ((x) + 2))) /* -1 => 1, 0 => 2 */
 
-/* Because clearly Nethack needs more ways to specify alignment.
-   The Amask2msa AM_LAWFUL check needs to mask with AM_MASK to
-   strip off possible AM_SHRINE bit */
-#define Amask2msa(x) (((x) & AM_MASK) == 4 ? 3 : (x) & AM_MASK)
-#define Msa2amask(x) ((x) == 3 ? 4 : (x))
+/* Because clearly Nethack needs more ways to specify alignment...
+   Amask2msa(): 1, 2, 4 converted to 1, 2, 3 to fit within a width 2 bitfield;
+   Msa2amask(): 1, 2, 3 converted back to 1, 2, 4;
+   For Amask2msa(), 'x' might have the shrine bit set so strip that off. */
+#define Amask2msa(x) ((((x) & AM_MASK) == 4) ? 3 : (x) & AM_MASK)
+#define Msa2amask(x) (((x) == 3) ? 4 : (x))
 #define MSA_NONE    0  /* unaligned or multiple alignments */
-#define MSA_LAWFUL  1
-#define MSA_NEUTRAL 2
-#define MSA_CHAOTIC 3
 
 #endif /* ALIGN_H */
diff --git a/src/dungeon.c b/src/dungeon.c
index 17a5ba3f1..e116073b9 100644
--- a/src/dungeon.c
+++ b/src/dungeon.c
@@ -1,4 +1,4 @@
-/* NetHack 3.7	dungeon.c	$NHDT-Date: 1596498164 2020/08/03 23:42:44 $  $NHDT-Branch: NetHack-3.7 $:$NHDT-Revision: 1.133 $ */
+/* NetHack 3.7	dungeon.c	$NHDT-Date: 1604105163 2020/10/31 00:46:03 $  $NHDT-Branch: NetHack-3.7 $:$NHDT-Revision: 1.135 $ */
 /* Copyright (c) Stichting Mathematisch Centrum, Amsterdam, 1985. */
 /*-Copyright (c) Robert Patrick Rankin, 2012. */
 /* NetHack may be freely redistributed.  See license for details. */
@@ -2842,10 +2842,13 @@ recalc_mapseen()
                     mptr->feat.ngrave = count;
                 break;
             case ALTAR:
+                /* get the altarmask for this location; might be a mimic */
+                atmp = altarmask_at(x, y);
+                /* convert to index: 0..3 */
                 atmp = (Is_astralevel(&u.uz)
                         && (levl[x][y].seenv & SVALL) != SVALL)
                          ? MSA_NONE
-                         : Amask2msa(levl[x][y].altarmask);
+                         : Amask2msa(atmp);
                 if (!mptr->feat.naltar)
                     mptr->feat.msalign = atmp;
                 else if (mptr->feat.msalign != atmp)
@@ -3297,6 +3300,8 @@ boolean printdun;
                         an(shop_string(mptr->feat.shoptype)));
         }
         if (mptr->feat.naltar > 0) {
+            unsigned atmp;
+
             /* Temples + non-temple altars get munged into just "altars" */
             if (mptr->feat.ntemple != mptr->feat.naltar)
                 ADDNTOBUF("altar", mptr->feat.naltar);
@@ -3304,7 +3309,9 @@ boolean printdun;
                 ADDNTOBUF("temple", mptr->feat.ntemple);
 
             /* only print out altar's god if they are all to your god */
-            if (Amask2align(Msa2amask(mptr->feat.msalign)) == u.ualign.type)
+            atmp = mptr->feat.msalign;              /*    0,  1,  2,  3 */
+            atmp = Msa2amask(atmp);                 /*    0,  1,  2,  4 */
+            if (Amask2align(atmp) == u.ualign.type) /* -127, -1,  0, +1 */
                 Sprintf(eos(buf), " to %s", align_gname(u.ualign.type));
         }
         ADDNTOBUF("throne", mptr->feat.nthrone);