diff --git a/library/alloc/src/macros.rs b/library/alloc/src/macros.rs
index 6ee3907cc8ea2..c000fd6f4efa7 100644
--- a/library/alloc/src/macros.rs
+++ b/library/alloc/src/macros.rs
@@ -48,8 +48,8 @@ macro_rules! vec {
     );
     ($($x:expr),+ $(,)?) => (
         <[_]>::into_vec(
-            // Using the intrinsic produces a dramatic improvement in compile
-            // time when constructing arrays with many elements.
+            // Using the intrinsic produces a dramatic improvement in stack usage for
+            // unoptimized programs using this code path to construct large Vecs.
             $crate::boxed::box_new([$($x),+])
         )
     );