diff --git a/src/libcore/iter/traits.rs b/src/libcore/iter/traits.rs
index 3415b0eea9bd0..34f14ef53f893 100644
--- a/src/libcore/iter/traits.rs
+++ b/src/libcore/iter/traits.rs
@@ -536,9 +536,9 @@ impl<'a, I: DoubleEndedIterator + ?Sized> DoubleEndedIterator for &'a mut I {
 /// #     }
 /// # }
 /// impl ExactSizeIterator for Counter {
-///     // We already have the number of iterations, so we can use it directly.
+///     // We can easily calculate the remaining number of iterations.
 ///     fn len(&self) -> usize {
-///         self.count
+///         5 - self.count
 ///     }
 /// }
 ///
@@ -546,7 +546,7 @@ impl<'a, I: DoubleEndedIterator + ?Sized> DoubleEndedIterator for &'a mut I {
 ///
 /// let counter = Counter::new();
 ///
-/// assert_eq!(0, counter.len());
+/// assert_eq!(5, counter.len());
 /// ```
 #[stable(feature = "rust1", since = "1.0.0")]
 pub trait ExactSizeIterator: Iterator {