diff --git a/src/vec-final.md b/src/vec-final.md
index 66c8e8b..d8aec0f 100644
--- a/src/vec-final.md
+++ b/src/vec-final.md
@@ -3,7 +3,6 @@
 ```rust
 #![feature(ptr_internals)]
 #![feature(allocator_api)]
-#![feature(alloc_layout_extra)]
 
 use std::ptr::{Unique, NonNull, self};
 use std::mem;