diff --git a/src/librustc/ty/mod.rs b/src/librustc/ty/mod.rs
index 4b9117f71be5c..d2dc07374ed00 100644
--- a/src/librustc/ty/mod.rs
+++ b/src/librustc/ty/mod.rs
@@ -600,7 +600,8 @@ impl<'tcx> rustc_serialize::UseSpecializedDecodable for Ty<'tcx> {}
 pub type CanonicalTy<'tcx> = Canonical<'tcx, Ty<'tcx>>;
 
 extern {
-    /// A dummy type used to force `List` to by unsized without requiring fat pointers.
+    /// A dummy type used to force `List` to be unsized while not requiring references to it be wide
+    /// pointers.
     type OpaqueListContents;
 }