diff --git a/src/libarena/lib.rs b/src/libarena/lib.rs
index d6bec816e4ee6..1739b2236e89d 100644
--- a/src/libarena/lib.rs
+++ b/src/libarena/lib.rs
@@ -13,6 +13,7 @@
 
 #![deny(rust_2018_idioms)]
 #![deny(internal)]
+#![deny(unused_lifetimes)]
 
 #![feature(core_intrinsics)]
 #![feature(dropck_eyepatch)]
diff --git a/src/libfmt_macros/lib.rs b/src/libfmt_macros/lib.rs
index 6fed83021609d..1000f237e8432 100644
--- a/src/libfmt_macros/lib.rs
+++ b/src/libfmt_macros/lib.rs
@@ -10,6 +10,7 @@
 
 #![deny(rust_2018_idioms)]
 #![deny(internal)]
+#![deny(unused_lifetimes)]
 
 #![feature(nll)]
 #![feature(rustc_private)]
diff --git a/src/librustc_allocator/lib.rs b/src/librustc_allocator/lib.rs
index 3aef5a76a3a05..e7a70895a3023 100644
--- a/src/librustc_allocator/lib.rs
+++ b/src/librustc_allocator/lib.rs
@@ -3,6 +3,7 @@
 
 #![deny(rust_2018_idioms)]
 #![deny(internal)]
+#![deny(unused_lifetimes)]
 
 pub mod expand;
 
diff --git a/src/librustc_driver/lib.rs b/src/librustc_driver/lib.rs
index 02f8eee67b151..5fb6ed31b0693 100644
--- a/src/librustc_driver/lib.rs
+++ b/src/librustc_driver/lib.rs
@@ -18,6 +18,7 @@
 
 #![deny(rust_2018_idioms)]
 #![deny(internal)]
+#![deny(unused_lifetimes)]
 
 pub extern crate getopts;
 #[cfg(unix)]
diff --git a/src/librustc_errors/lib.rs b/src/librustc_errors/lib.rs
index cc3180c783bdf..27bd30e8afd89 100644
--- a/src/librustc_errors/lib.rs
+++ b/src/librustc_errors/lib.rs
@@ -6,6 +6,7 @@
 #![feature(optin_builtin_traits)]
 #![deny(rust_2018_idioms)]
 #![deny(internal)]
+#![deny(unused_lifetimes)]
 
 #[allow(unused_extern_crates)]
 extern crate serialize as rustc_serialize; // used by deriving
diff --git a/src/librustc_interface/lib.rs b/src/librustc_interface/lib.rs
index d1e2a1a4ad506..7fc311d40c3d0 100644
--- a/src/librustc_interface/lib.rs
+++ b/src/librustc_interface/lib.rs
@@ -8,6 +8,7 @@
 
 #![deny(rust_2018_idioms)]
 #![deny(internal)]
+#![deny(unused_lifetimes)]
 
 #![allow(unused_imports)]
 
diff --git a/src/librustc_metadata/lib.rs b/src/librustc_metadata/lib.rs
index e0b92341575cc..e49ca8acf6702 100644
--- a/src/librustc_metadata/lib.rs
+++ b/src/librustc_metadata/lib.rs
@@ -16,6 +16,7 @@
 
 #![deny(rust_2018_idioms)]
 #![deny(internal)]
+#![deny(unused_lifetimes)]
 
 extern crate libc;
 #[allow(unused_extern_crates)]
diff --git a/src/librustc_passes/lib.rs b/src/librustc_passes/lib.rs
index 7c48feecb2110..fbd6ddf84c33a 100644
--- a/src/librustc_passes/lib.rs
+++ b/src/librustc_passes/lib.rs
@@ -13,6 +13,7 @@
 
 #![deny(rust_2018_idioms)]
 #![deny(internal)]
+#![deny(unused_lifetimes)]
 
 #[macro_use]
 extern crate rustc;
diff --git a/src/librustc_privacy/lib.rs b/src/librustc_privacy/lib.rs
index 6d01328cd16e6..42b70dd181b3c 100644
--- a/src/librustc_privacy/lib.rs
+++ b/src/librustc_privacy/lib.rs
@@ -2,6 +2,7 @@
 
 #![deny(rust_2018_idioms)]
 #![deny(internal)]
+#![deny(unused_lifetimes)]
 
 #![feature(nll)]
 #![feature(rustc_diagnostic_macros)]
diff --git a/src/librustc_resolve/lib.rs b/src/librustc_resolve/lib.rs
index 18f3c0285c210..fec7bf3b273ee 100644
--- a/src/librustc_resolve/lib.rs
+++ b/src/librustc_resolve/lib.rs
@@ -12,6 +12,7 @@
 
 #![deny(rust_2018_idioms)]
 #![deny(internal)]
+#![deny(unused_lifetimes)]
 
 pub use rustc::hir::def::{Namespace, PerNS};
 
diff --git a/src/librustc_save_analysis/lib.rs b/src/librustc_save_analysis/lib.rs
index cda6b60b76790..30b0250cec182 100644
--- a/src/librustc_save_analysis/lib.rs
+++ b/src/librustc_save_analysis/lib.rs
@@ -2,6 +2,7 @@
 #![feature(nll)]
 #![deny(rust_2018_idioms)]
 #![deny(internal)]
+#![deny(unused_lifetimes)]
 #![allow(unused_attributes)]
 
 #![recursion_limit="256"]
diff --git a/src/librustc_typeck/lib.rs b/src/librustc_typeck/lib.rs
index 30993b86a385f..14dec423c57a9 100644
--- a/src/librustc_typeck/lib.rs
+++ b/src/librustc_typeck/lib.rs
@@ -72,6 +72,7 @@ This API is completely unstable and subject to change.
 
 #![deny(rust_2018_idioms)]
 #![deny(internal)]
+#![deny(unused_lifetimes)]
 #![allow(explicit_outlives_requirements)]
 
 #[macro_use] extern crate log;
diff --git a/src/libsyntax/lib.rs b/src/libsyntax/lib.rs
index c69364d4e19bb..55db8da327673 100644
--- a/src/libsyntax/lib.rs
+++ b/src/libsyntax/lib.rs
@@ -9,6 +9,7 @@
 
 #![deny(rust_2018_idioms)]
 #![deny(internal)]
+#![deny(unused_lifetimes)]
 
 #![feature(bind_by_move_pattern_guards)]
 #![feature(crate_visibility_modifier)]
diff --git a/src/libsyntax_pos/lib.rs b/src/libsyntax_pos/lib.rs
index 8f5595968a738..649ab81198d2a 100644
--- a/src/libsyntax_pos/lib.rs
+++ b/src/libsyntax_pos/lib.rs
@@ -8,6 +8,7 @@
 
 #![deny(rust_2018_idioms)]
 #![deny(internal)]
+#![deny(unused_lifetimes)]
 
 #![feature(const_fn)]
 #![feature(crate_visibility_modifier)]