diff --git a/src/libstd/macros.rs b/src/libstd/macros.rs
index 03d2a307216..37e88ee6209 100644
--- a/src/libstd/macros.rs
+++ b/src/libstd/macros.rs
@@ -232,7 +232,8 @@ macro_rules! eprintln {
 /// for some expression `expr`.
 ///
 /// The `dbg!` macro works exactly the same in release builds.
-/// This is useful when debugging issues that only occur in release builds or when debugging in
+/// This is useful when debugging issues that only occur in release
+/// builds or when debugging in release mode is significantly faster.
 /// release mode is significantly faster.
 ///
 /// Note that the macro is intended as a debugging tool and therefore you