diff --git a/src/libcore/macros.rs b/src/libcore/macros.rs
index 1d0ac42de601..6d7e1938cfde 100644
--- a/src/libcore/macros.rs
+++ b/src/libcore/macros.rs
@@ -354,7 +354,7 @@ macro_rules! try {
 /// In a no_std setup you are responsible for the
 /// implementation details of the components.
 ///
-/// ```
+/// ```no_run
 ///  # extern crate core;
 ///  use core::fmt::Write;
 ///