diff --git a/src/doc/book/trait-objects.md b/src/doc/book/trait-objects.md
index 71536f409e8f..00a841a75db8 100644
--- a/src/doc/book/trait-objects.md
+++ b/src/doc/book/trait-objects.md
@@ -263,8 +263,7 @@ any resources of the vtable’s type: for `u8` it is trivial, but for `String` i
 will free the memory. This is necessary for owning trait objects like
 `Box<Foo>`, which need to clean-up both the `Box` allocation as well as the
 internal type when they go out of scope. The `size` and `align` fields store
-the size of the erased type, and its alignment requirements; these are
-used by the `std::mem::size_of_val` and `std::mem::align_of_val` functions.
+the size of the erased type, and its alignment requirements.
 
 Suppose we’ve got some values that implement `Foo`. The explicit form of
 construction and use of `Foo` trait objects might look a bit like (ignoring the