diff --git a/src/dig.c b/src/dig.c
index 7ea05bc07..93c64c5bf 100644
--- a/src/dig.c
+++ b/src/dig.c
@@ -194,8 +194,8 @@ dig_check(struct monst *madeby, boolean verbose, coordxy x, coordxy y)
             pline_The("throne is too hard to break apart.");
         return FALSE;
     } else if (IS_ALTAR(levl[x][y].typ)
-               && (madeby != BY_OBJECT || Is_astralevel(&u.uz)
-                   || Is_sanctum(&u.uz))) {
+               && (madeby != BY_OBJECT
+                   || (altarmask_at(x, y) & AM_SANCTUM) != 0)) {
         if (verbose)
             pline_The("altar is too hard to break apart.");
         return FALSE;
diff --git a/src/trap.c b/src/trap.c
index 0989ed7da..77a99ea0d 100644
--- a/src/trap.c
+++ b/src/trap.c
@@ -470,8 +470,9 @@ maketrap(coordxy x, coordxy y, int typ)
                 || (u.utraptype == TT_LAVA && !is_lava(x, y))))
             reset_utrap(FALSE);
         /* old <tx,ty> remain valid */
-    } else if ((IS_FURNITURE(lev->typ)
-                && (!IS_GRAVE(lev->typ) || (typ != PIT && typ != HOLE)))
+    } else if (!CAN_OVERWRITE_TERRAIN(lev->typ)
+               || (IS_FURNITURE(lev->typ)
+                   && (typ != PIT && typ != HOLE))
                || is_pool_or_lava(x, y)
                || (IS_AIR(lev->typ) && typ != MAGIC_PORTAL)
                || (typ == LEVEL_TELEP && single_level_branch(&u.uz))) {