diff --git a/src/doc/unstable-book/src/language-features/trait-upcasting.md b/src/doc/unstable-book/src/language-features/trait-upcasting.md
index 3697ae38f9d81..a5f99cc86f270 100644
--- a/src/doc/unstable-book/src/language-features/trait-upcasting.md
+++ b/src/doc/unstable-book/src/language-features/trait-upcasting.md
@@ -12,7 +12,6 @@ so long as `Bar: Foo`.
 
 ```rust,edition2018
 #![feature(trait_upcasting)]
-#![allow(incomplete_features)]
 
 trait Foo {}