diff --git a/src/test/ui/async-await/async-fn-size.rs b/src/test/ui/async-await/async-fn-size.rs
index e4dfd4d829e..c6b2ed13b0a 100644
--- a/src/test/ui/async-await/async-fn-size.rs
+++ b/src/test/ui/async-await/async-fn-size.rs
@@ -1,5 +1,5 @@
 // run-pass
-
+// aux-build:arc_wake.rs
 // edition:2018
 
 #![feature(async_await)]