diff --git a/src/librustc/lint/builtin.rs b/src/librustc/lint/builtin.rs
index ed94e5fe377c4..173f8d496990a 100644
--- a/src/librustc/lint/builtin.rs
+++ b/src/librustc/lint/builtin.rs
@@ -114,7 +114,7 @@ declare_lint! {
 
 declare_lint! {
     pub PRIVATE_IN_PUBLIC,
-    Deny,
+    Warn,
     "detect private items in public interfaces not caught by the old implementation"
 }
 
diff --git a/src/librustc_privacy/diagnostics.rs b/src/librustc_privacy/diagnostics.rs
index 891b6adea7893..66afe5835bf6f 100644
--- a/src/librustc_privacy/diagnostics.rs
+++ b/src/librustc_privacy/diagnostics.rs
@@ -17,6 +17,8 @@ A private trait was used on a public type parameter bound. Erroneous code
 examples:
 
 ```compile_fail,E0445
+#![deny(private_in_public)]
+
 trait Foo {
     fn dummy(&self) { }
 }
@@ -45,6 +47,8 @@ E0446: r##"
 A private type was used in a public type signature. Erroneous code example:
 
 ```compile_fail,E0446
+#![deny(private_in_public)]
+
 mod Foo {
     struct Bar(u32);
 
diff --git a/src/test/compile-fail/issue-28514.rs b/src/test/compile-fail/issue-28514.rs
index 6ee375503c2af..fb25166531dcb 100644
--- a/src/test/compile-fail/issue-28514.rs
+++ b/src/test/compile-fail/issue-28514.rs
@@ -8,6 +8,8 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
+#![deny(private_in_public)]
+
 pub use inner::C;
 
 mod inner {
diff --git a/src/test/compile-fail/issue-30079.rs b/src/test/compile-fail/issue-30079.rs
index 55c58ed021b27..6a54e53f14638 100644
--- a/src/test/compile-fail/issue-30079.rs
+++ b/src/test/compile-fail/issue-30079.rs
@@ -8,6 +8,7 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
+#![deny(private_in_public)]
 #![allow(unused)]
 
 struct SemiPriv;
diff --git a/src/test/compile-fail/private-in-public-warn.rs b/src/test/compile-fail/private-in-public-warn.rs
index 6d6af77be92b0..455de37aee96f 100644
--- a/src/test/compile-fail/private-in-public-warn.rs
+++ b/src/test/compile-fail/private-in-public-warn.rs
@@ -13,8 +13,8 @@
 
 #![feature(associated_consts)]
 #![feature(associated_type_defaults)]
-#![allow(dead_code)]
-#![allow(unused_variables)]
+#![deny(private_in_public)]
+#![allow(unused)]
 #![allow(improper_ctypes)]
 
 mod types {
diff --git a/src/test/compile-fail/private-variant-and-crate-reexport.rs b/src/test/compile-fail/private-variant-and-crate-reexport.rs
index ce029e7eff7fc..dce533e73feea 100644
--- a/src/test/compile-fail/private-variant-and-crate-reexport.rs
+++ b/src/test/compile-fail/private-variant-and-crate-reexport.rs
@@ -8,6 +8,7 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
+#![deny(private_in_public)]
 #![allow(dead_code)]
 
 extern crate core;