diff --git a/src/libstd/sys/unix/ext/mod.rs b/src/libstd/sys/unix/ext/mod.rs
index 8039dcd2208cb..78a3fd05c730a 100644
--- a/src/libstd/sys/unix/ext/mod.rs
+++ b/src/libstd/sys/unix/ext/mod.rs
@@ -15,11 +15,13 @@
 //! use std::fs::File;
 //! use std::os::unix::prelude::*;
 //!
-//! fn main() {
+//! fn main() -> std::io::Result<()> {
 //!     let f = File::create("foo.txt")?;
 //!     let fd = f.as_raw_fd();
 //!
 //!     // use fd with native unix bindings
+//!
+//!     Ok(())
 //! }
 //! ```