diff --git a/extra/game/worlds/worlds.factor b/extra/game/worlds/worlds.factor
index a04ac3f195..b327846d94 100644
--- a/extra/game/worlds/worlds.factor
+++ b/extra/game/worlds/worlds.factor
@@ -1,8 +1,8 @@
 ! (c)2009 Joe Groff bsd license
-USING: accessors audio.engine combinators destructors fry
-game.input game.loop generic kernel math parser sequences
-threads ui ui.gadgets ui.gadgets.worlds ui.gestures words
-words.constant ;
+USING: accessors audio.engine combinators concurrency.promises
+destructors fry game.input game.loop generic kernel math parser
+sequences threads ui ui.gadgets ui.gadgets.worlds ui.gestures
+words words.constant ;
 IN: game.worlds
 
 TUPLE: game-world < world