diff --git a/src/libstd/thread/local.rs b/src/libstd/thread/local.rs
index 3a876e05eccbd..7ad6b124e3a38 100644
--- a/src/libstd/thread/local.rs
+++ b/src/libstd/thread/local.rs
@@ -40,13 +40,16 @@ use crate::mem;
 /// });
 ///
 /// // each thread starts out with the initial value of 1
-/// thread::spawn(move|| {
+/// let t = thread::spawn(move|| {
 ///     FOO.with(|f| {
 ///         assert_eq!(*f.borrow(), 1);
 ///         *f.borrow_mut() = 3;
 ///     });
 /// });
 ///
+/// // wait for the thread to complete and bail out on panic
+/// t.join().unwrap();
+///
 /// // we retain our original value of 2 despite the child thread
 /// FOO.with(|f| {
 ///     assert_eq!(*f.borrow(), 2);