diff --git a/src/build_helper/lib.rs b/src/build_helper/lib.rs
index 2f9953330f4..4d767f09689 100644
--- a/src/build_helper/lib.rs
+++ b/src/build_helper/lib.rs
@@ -8,6 +8,8 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
+#![deny(bare_trait_objects)]
+
 use std::fs::File;
 use std::path::{Path, PathBuf};
 use std::process::{Command, Stdio};
diff --git a/src/liballoc_jemalloc/lib.rs b/src/liballoc_jemalloc/lib.rs
index b3b20715511..413b212281b 100644
--- a/src/liballoc_jemalloc/lib.rs
+++ b/src/liballoc_jemalloc/lib.rs
@@ -10,6 +10,7 @@
 
 #![no_std]
 #![allow(unused_attributes)]
+#![deny(bare_trait_objects)]
 #![unstable(feature = "alloc_jemalloc",
             reason = "implementation detail of std, does not provide any public API",
             issue = "0")]
diff --git a/src/liballoc_system/lib.rs b/src/liballoc_system/lib.rs
index 64348e05de7..c6c0abefbab 100644
--- a/src/liballoc_system/lib.rs
+++ b/src/liballoc_system/lib.rs
@@ -10,6 +10,7 @@
 
 #![no_std]
 #![allow(unused_attributes)]
+#![deny(bare_trait_objects)]
 #![unstable(feature = "alloc_system",
             reason = "this library is unlikely to be stabilized in its current \
                       form or name",
diff --git a/src/libarena/lib.rs b/src/libarena/lib.rs
index 0f4a5d16e17..6f692923c85 100644
--- a/src/libarena/lib.rs
+++ b/src/libarena/lib.rs
@@ -30,6 +30,7 @@
 #![cfg_attr(test, feature(test))]
 
 #![allow(deprecated)]
+#![deny(bare_trait_objects)]
 
 extern crate alloc;
 extern crate rustc_data_structures;
diff --git a/src/libfmt_macros/lib.rs b/src/libfmt_macros/lib.rs
index a77751d65d0..51c3efb41ad 100644
--- a/src/libfmt_macros/lib.rs
+++ b/src/libfmt_macros/lib.rs
@@ -14,6 +14,8 @@
 //! Parsing does not happen at runtime: structures of `std::fmt::rt` are
 //! generated instead.
 
+#![deny(bare_trait_objects)]
+
 #![doc(html_logo_url = "https://www.rust-lang.org/logos/rust-logo-128x128-blk-v2.png",
        html_favicon_url = "https://doc.rust-lang.org/favicon.ico",
        html_root_url = "https://doc.rust-lang.org/nightly/",
diff --git a/src/libgraphviz/lib.rs b/src/libgraphviz/lib.rs
index 158d0101515..9e71ed4063e 100644
--- a/src/libgraphviz/lib.rs
+++ b/src/libgraphviz/lib.rs
@@ -283,6 +283,8 @@
 //!
 //! * [DOT language](http://www.graphviz.org/doc/info/lang.html)
 
+#![deny(bare_trait_objects)]
+
 #![doc(html_logo_url = "https://www.rust-lang.org/logos/rust-logo-128x128-blk-v2.png",
        html_favicon_url = "https://doc.rust-lang.org/favicon.ico",
        html_root_url = "https://doc.rust-lang.org/nightly/",
diff --git a/src/libpanic_abort/lib.rs b/src/libpanic_abort/lib.rs
index 392bf17968f..02ab28507d7 100644
--- a/src/libpanic_abort/lib.rs
+++ b/src/libpanic_abort/lib.rs
@@ -21,6 +21,7 @@
        issue_tracker_base_url = "https://github.com/rust-lang/rust/issues/")]
 #![panic_runtime]
 #![allow(unused_features)]
+#![deny(bare_trait_objects)]
 
 #![feature(core_intrinsics)]
 #![feature(libc)]
diff --git a/src/libproc_macro/lib.rs b/src/libproc_macro/lib.rs
index 876cf295acc..7c0cf9eadde 100644
--- a/src/libproc_macro/lib.rs
+++ b/src/libproc_macro/lib.rs
@@ -22,6 +22,7 @@
 //! See [the book](../book/first-edition/procedural-macros.html) for more.
 
 #![stable(feature = "proc_macro_lib", since = "1.15.0")]
+#![deny(bare_trait_objects)]
 #![deny(missing_docs)]
 #![doc(html_logo_url = "https://www.rust-lang.org/logos/rust-logo-128x128-blk-v2.png",
        html_favicon_url = "https://doc.rust-lang.org/favicon.ico",
diff --git a/src/libprofiler_builtins/lib.rs b/src/libprofiler_builtins/lib.rs
index 6d0d6d115b7..3d91505cd77 100644
--- a/src/libprofiler_builtins/lib.rs
+++ b/src/libprofiler_builtins/lib.rs
@@ -15,4 +15,5 @@
             reason = "internal implementation detail of rustc right now",
             issue = "0")]
 #![allow(unused_features)]
+#![deny(bare_trait_objects)]
 #![feature(staged_api)]
diff --git a/src/librustc_apfloat/lib.rs b/src/librustc_apfloat/lib.rs
index 08438805a70..c7cd958016d 100644
--- a/src/librustc_apfloat/lib.rs
+++ b/src/librustc_apfloat/lib.rs
@@ -40,6 +40,8 @@
 //!
 //! This API is completely unstable and subject to change.
 
+#![deny(bare_trait_objects)]
+
 #![doc(html_logo_url = "https://www.rust-lang.org/logos/rust-logo-128x128-blk-v2.png",
       html_favicon_url = "https://doc.rust-lang.org/favicon.ico",
       html_root_url = "https://doc.rust-lang.org/nightly/")]
diff --git a/src/librustc_asan/lib.rs b/src/librustc_asan/lib.rs
index 0c78fd74a23..7bd1e98f85d 100644
--- a/src/librustc_asan/lib.rs
+++ b/src/librustc_asan/lib.rs
@@ -8,6 +8,8 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
+#![deny(bare_trait_objects)]
+
 #![sanitizer_runtime]
 #![feature(alloc_system)]
 #![feature(sanitizer_runtime)]
diff --git a/src/librustc_borrowck/lib.rs b/src/librustc_borrowck/lib.rs
index a5a20af0e4e..d583a32c431 100644
--- a/src/librustc_borrowck/lib.rs
+++ b/src/librustc_borrowck/lib.rs
@@ -13,6 +13,7 @@
       html_root_url = "https://doc.rust-lang.org/nightly/")]
 
 #![allow(non_camel_case_types)]
+#![deny(bare_trait_objects)]
 
 #![feature(from_ref)]
 #![feature(quote)]
diff --git a/src/librustc_incremental/lib.rs b/src/librustc_incremental/lib.rs
index 3839c133a6e..2ef88041d33 100644
--- a/src/librustc_incremental/lib.rs
+++ b/src/librustc_incremental/lib.rs
@@ -10,6 +10,8 @@
 
 //! Support for serializing the dep-graph and reloading it.
 
+#![deny(bare_trait_objects)]
+
 #![doc(html_logo_url = "https://www.rust-lang.org/logos/rust-logo-128x128-blk-v2.png",
       html_favicon_url = "https://doc.rust-lang.org/favicon.ico",
       html_root_url = "https://doc.rust-lang.org/nightly/")]
diff --git a/src/librustc_lint/lib.rs b/src/librustc_lint/lib.rs
index 359b056b5a2..9f8ef6ef432 100644
--- a/src/librustc_lint/lib.rs
+++ b/src/librustc_lint/lib.rs
@@ -19,6 +19,8 @@
 //!
 //! This API is completely unstable and subject to change.
 
+#![deny(bare_trait_objects)]
+
 #![doc(html_logo_url = "https://www.rust-lang.org/logos/rust-logo-128x128-blk-v2.png",
       html_favicon_url = "https://doc.rust-lang.org/favicon.ico",
       html_root_url = "https://doc.rust-lang.org/nightly/")]
diff --git a/src/librustc_llvm/lib.rs b/src/librustc_llvm/lib.rs
index 741758cb954..c60016cde0d 100644
--- a/src/librustc_llvm/lib.rs
+++ b/src/librustc_llvm/lib.rs
@@ -12,6 +12,7 @@
 #![allow(non_camel_case_types)]
 #![allow(non_snake_case)]
 #![allow(dead_code)]
+#![deny(bare_trait_objects)]
 
 #![doc(html_logo_url = "https://www.rust-lang.org/logos/rust-logo-128x128-blk-v2.png",
        html_favicon_url = "https://doc.rust-lang.org/favicon.ico",
diff --git a/src/librustc_lsan/lib.rs b/src/librustc_lsan/lib.rs
index 0c78fd74a23..7bd1e98f85d 100644
--- a/src/librustc_lsan/lib.rs
+++ b/src/librustc_lsan/lib.rs
@@ -8,6 +8,8 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
+#![deny(bare_trait_objects)]
+
 #![sanitizer_runtime]
 #![feature(alloc_system)]
 #![feature(sanitizer_runtime)]
diff --git a/src/librustc_mir/lib.rs b/src/librustc_mir/lib.rs
index dc0d0b24463..c042c68d40b 100644
--- a/src/librustc_mir/lib.rs
+++ b/src/librustc_mir/lib.rs
@@ -14,6 +14,8 @@ Rust MIR: a lowered representation of Rust. Also: an experiment!
 
 */
 
+#![deny(bare_trait_objects)]
+
 #![feature(slice_patterns)]
 #![feature(slice_sort_by_cached_key)]
 #![feature(from_ref)]
diff --git a/src/librustc_msan/lib.rs b/src/librustc_msan/lib.rs
index 0c78fd74a23..7bd1e98f85d 100644
--- a/src/librustc_msan/lib.rs
+++ b/src/librustc_msan/lib.rs
@@ -8,6 +8,8 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
+#![deny(bare_trait_objects)]
+
 #![sanitizer_runtime]
 #![feature(alloc_system)]
 #![feature(sanitizer_runtime)]
diff --git a/src/librustc_passes/lib.rs b/src/librustc_passes/lib.rs
index 41f1e782965..15d7c0fdaa3 100644
--- a/src/librustc_passes/lib.rs
+++ b/src/librustc_passes/lib.rs
@@ -14,6 +14,8 @@
 //!
 //! This API is completely unstable and subject to change.
 
+#![deny(bare_trait_objects)]
+
 #![doc(html_logo_url = "https://www.rust-lang.org/logos/rust-logo-128x128-blk-v2.png",
        html_favicon_url = "https://doc.rust-lang.org/favicon.ico",
        html_root_url = "https://doc.rust-lang.org/nightly/")]
diff --git a/src/librustc_platform_intrinsics/lib.rs b/src/librustc_platform_intrinsics/lib.rs
index b57debdd994..92e83fd70fa 100644
--- a/src/librustc_platform_intrinsics/lib.rs
+++ b/src/librustc_platform_intrinsics/lib.rs
@@ -9,6 +9,7 @@
 // except according to those terms.
 
 #![allow(bad_style)]
+#![deny(bare_trait_objects)]
 
 pub struct Intrinsic {
     pub inputs: &'static [&'static Type],
diff --git a/src/librustc_plugin/lib.rs b/src/librustc_plugin/lib.rs
index 348aa6a7cef..b2c492f204f 100644
--- a/src/librustc_plugin/lib.rs
+++ b/src/librustc_plugin/lib.rs
@@ -60,6 +60,8 @@
 //! See the [`plugin` feature](../unstable-book/language-features/plugin.html) of
 //! the Unstable Book for more examples.
 
+#![deny(bare_trait_objects)]
+
 #![doc(html_logo_url = "https://www.rust-lang.org/logos/rust-logo-128x128-blk-v2.png",
        html_favicon_url = "https://doc.rust-lang.org/favicon.ico",
        html_root_url = "https://doc.rust-lang.org/nightly/")]
diff --git a/src/librustc_privacy/lib.rs b/src/librustc_privacy/lib.rs
index 3919ba13076..f69e664ea46 100644
--- a/src/librustc_privacy/lib.rs
+++ b/src/librustc_privacy/lib.rs
@@ -8,6 +8,8 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
+#![deny(bare_trait_objects)]
+
 #![doc(html_logo_url = "https://www.rust-lang.org/logos/rust-logo-128x128-blk-v2.png",
        html_favicon_url = "https://doc.rust-lang.org/favicon.ico",
        html_root_url = "https://doc.rust-lang.org/nightly/")]
diff --git a/src/librustc_traits/lib.rs b/src/librustc_traits/lib.rs
index 1da3907915a..cd55b5ddc5b 100644
--- a/src/librustc_traits/lib.rs
+++ b/src/librustc_traits/lib.rs
@@ -11,6 +11,8 @@
 //! New recursive solver modeled on Chalk's recursive solver. Most of
 //! the guts are broken up into modules; see the comments in those modules.
 
+#![deny(bare_trait_objects)]
+
 #![feature(crate_in_paths)]
 #![feature(crate_visibility_modifier)]
 #![feature(extern_prelude)]
diff --git a/src/librustc_tsan/lib.rs b/src/librustc_tsan/lib.rs
index 0c78fd74a23..7bd1e98f85d 100644
--- a/src/librustc_tsan/lib.rs
+++ b/src/librustc_tsan/lib.rs
@@ -8,6 +8,8 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
+#![deny(bare_trait_objects)]
+
 #![sanitizer_runtime]
 #![feature(alloc_system)]
 #![feature(sanitizer_runtime)]
diff --git a/src/libsyntax_pos/lib.rs b/src/libsyntax_pos/lib.rs
index 61af70af47d..cc09a944e4c 100644
--- a/src/libsyntax_pos/lib.rs
+++ b/src/libsyntax_pos/lib.rs
@@ -14,6 +14,8 @@
 //!
 //! This API is completely unstable and subject to change.
 
+#![deny(bare_trait_objects)]
+
 #![doc(html_logo_url = "https://www.rust-lang.org/logos/rust-logo-128x128-blk-v2.png",
       html_favicon_url = "https://doc.rust-lang.org/favicon.ico",
       html_root_url = "https://doc.rust-lang.org/nightly/")]
diff --git a/src/libunwind/lib.rs b/src/libunwind/lib.rs
index 2b3c19c067e..ea5eee3cc7d 100644
--- a/src/libunwind/lib.rs
+++ b/src/libunwind/lib.rs
@@ -8,6 +8,8 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
+#![deny(bare_trait_objects)]
+
 #![no_std]
 #![unstable(feature = "panic_unwind", issue = "32837")]