diff --git a/src/Lobby.hh b/src/Lobby.hh
index 9d5e3c5f..f0c5fa14 100644
--- a/src/Lobby.hh
+++ b/src/Lobby.hh
@@ -76,7 +76,8 @@ struct Lobby : public std::enable_shared_from_this<Lobby> {
     SPECTATORS_FORBIDDEN            = 0x00008000,
     START_BATTLE_PLAYER_IMMEDIATELY = 0x00010000,
     CANNOT_CHANGE_CHEAT_MODE        = 0x00020000,
-    USE_CREATOR_SECTION_ID          = 0x00040000,
+    CANNOT_CHANGE_DROP_MODE         = 0x00040000,
+    USE_CREATOR_SECTION_ID          = 0x00080000,
     // Flags used only for lobbies
     PUBLIC                          = 0x01000000,
     DEFAULT                         = 0x02000000,
diff --git a/src/ReceiveSubcommands.cc b/src/ReceiveSubcommands.cc
index 788f807d..b9220a35 100644
--- a/src/ReceiveSubcommands.cc
+++ b/src/ReceiveSubcommands.cc
@@ -4375,6 +4375,8 @@ static void on_photon_crystal_exchange_bb(shared_ptr<Client> c, uint8_t, uint8_t
     size_t index = p->inventory.find_item_by_primary_identifier(0x03100200);
     auto item = p->remove_item(p->inventory.items[index].data.id, 1, *s->item_stack_limits(c->version()));
     send_destroy_item_to_lobby(c, item.id, 1);
+    l->set_drop_mode(Lobby::DropMode::DISABLED);
+    l->allowed_drop_modes = (1 << static_cast<uint8_t>(l->drop_mode)); // DISABLED only
   }
 }