diff --git a/util/async.lua b/util/async.lua
index 52d2c99c1..8b92c878d 100644
--- a/util/async.lua
+++ b/util/async.lua
@@ -233,7 +233,6 @@ local function sleep(s)
 end
 
 return {
-	once = once;
 	ready = ready;
 	waiter = waiter;
 	guarder = guarder;