3 files changed, 2 insertions, 2 deletions
diff --git a/src/libstd/lib.rs b/src/libstd/lib.rs
index cf1eb5cd52e..b57067e35e9 100644
--- a/src/libstd/lib.rs
+++ b/src/libstd/lib.rs
@@ -358,6 +358,7 @@ extern crate std_unicode;
 extern crate libc;
 
 // We always need an unwinder currently for backtraces
+#[allow(unused_extern_crates)]
 extern crate unwind;
 
 // compiler-rt intrinsics
diff --git a/src/libstd/prelude/mod.rs b/src/libstd/prelude/mod.rs
index 49cdba21a1d..538753d8692 100644
--- a/src/libstd/prelude/mod.rs
+++ b/src/libstd/prelude/mod.rs
@@ -23,6 +23,7 @@
 //! On a technical level, Rust inserts
 //!
 //! ```
+//! # #[allow(unused_extern_crates)]
 //! extern crate std;
 //! ```
 //!
diff --git a/src/libstd/sys/unix/ext/fs.rs b/src/libstd/sys/unix/ext/fs.rs
index a94585723a1..f44b9aa9615 100644
--- a/src/libstd/sys/unix/ext/fs.rs
+++ b/src/libstd/sys/unix/ext/fs.rs
@@ -154,8 +154,6 @@ pub trait OpenOptionsExt {
     /// # Examples
     ///
     /// ```no_run
-    /// # #![feature(libc)]
-    /// extern crate libc;
     /// use std::fs::OpenOptions;
     /// use std::os::unix::fs::OpenOptionsExt;
     ///