diff --git a/Cargo.toml b/Cargo.toml
index f68251adb5eab..8c70bb1893972 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -61,4 +61,5 @@ rustc-workspace-hack = "1.0.0"
 rustc_tools_util = { version = "0.2.0", path = "rustc_tools_util"}
 
 [features]
+deny-warnings = []
 debugging = []
diff --git a/ci/base-tests.sh b/ci/base-tests.sh
index a53a0ea52be62..d91d553147cd1 100755
--- a/ci/base-tests.sh
+++ b/ci/base-tests.sh
@@ -7,8 +7,8 @@ if [ "$TRAVIS_OS_NAME" == "linux" ]; then
   remark -f *.md -f doc/*.md > /dev/null
 fi
 # build clippy in debug mode and run tests
-cargo build --features debugging
-cargo test --features debugging
+cargo build --features "debugging deny-warnings"
+cargo test --features "debugging deny-warnings"
 # for faster build, share target dir between subcrates
 export CARGO_TARGET_DIR=`pwd`/target/
 (cd clippy_lints && cargo test)
diff --git a/clippy_lints/src/lib.rs b/clippy_lints/src/lib.rs
index 0d2c9e6b98704..369a736aa644c 100644
--- a/clippy_lints/src/lib.rs
+++ b/clippy_lints/src/lib.rs
@@ -9,6 +9,7 @@
 #![recursion_limit = "512"]
 #![warn(rust_2018_idioms, trivial_casts, trivial_numeric_casts)]
 #![deny(rustc::internal)]
+#![cfg_attr(feature = "deny-warnings", deny(warnings))]
 #![feature(crate_visibility_modifier)]
 #![feature(concat_idents)]
 
diff --git a/src/driver.rs b/src/driver.rs
index 545c43f9a45fe..146e3fe2d08f0 100644
--- a/src/driver.rs
+++ b/src/driver.rs
@@ -1,3 +1,4 @@
+#![cfg_attr(feature = "deny-warnings", deny(warnings))]
 #![feature(rustc_private)]
 
 // FIXME: switch to something more ergonomic here, once available.
diff --git a/src/main.rs b/src/main.rs
index e0b2bcc726645..8f9afb95337de 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -1,3 +1,5 @@
+#![cfg_attr(feature = "deny-warnings", deny(warnings))]
+
 use rustc_tools_util::*;
 
 const CARGO_CLIPPY_HELP: &str = r#"Checks a package to catch common mistakes and improve your Rust code.