1 files changed, 10 insertions, 0 deletions
diff --git a/crawl-ref/source/decks.cc b/crawl-ref/source/decks.cc
index fdcf348bf8..6797a503ed 100644
--- a/crawl-ref/source/decks.cc
+++ b/crawl-ref/source/decks.cc
@@ -1362,6 +1362,15 @@ static void _swap_monster_card(int power, deck_rarity_type rarity)
     {
         monsters& mon(*mon_to_swap);
         const coord_def newpos = mon.pos();
+
+        // Be nice: no swapping into uninhabitable environments.
+        if (is_grid_dangerous(grd(newpos))
+            || !monster_habitable_grid(mon_to_swap, grd(you.pos())))
+        {
+            mpr("You spin around.");
+            return;
+        }
+
         bool mon_caught = mons_is_caught(&mon);
         bool you_caught = you.attribute[ATTR_HELD];
 
@@ -1382,6 +1391,7 @@ static void _swap_monster_card(int power, deck_rarity_type rarity)
         }
 
         // Move you to its previous location.
+        // FIXME: this should also handle merfolk swimming, etc.
         you.moveto(newpos);
 
         if (mon_caught)