diff --git a/src/libcore/iter/iterator.rs b/src/libcore/iter/iterator.rs
index 8fb71295a88..6f5bb2747df 100644
--- a/src/libcore/iter/iterator.rs
+++ b/src/libcore/iter/iterator.rs
@@ -11,7 +11,6 @@
 use clone::Clone;
 use cmp::{Ord, PartialOrd, PartialEq, Ordering};
 use default::Default;
-use marker;
 use num::{Zero, One};
 use ops::{Add, FnMut, Mul};
 use option::Option::{self, Some, None};
@@ -1748,23 +1747,9 @@ pub trait Iterator {
         FromB: Default + Extend<B>,
         Self: Sized + Iterator<Item=(A, B)>,
     {
-        struct SizeHint<A>(usize, Option<usize>, marker::PhantomData<A>);
-        impl<A> Iterator for SizeHint<A> {
-            type Item = A;
-
-            fn next(&mut self) -> Option<A> { None }
-            fn size_hint(&self) -> (usize, Option<usize>) {
-                (self.0, self.1)
-            }
-        }
-
-        let (lo, hi) = self.size_hint();
         let mut ts: FromA = Default::default();
         let mut us: FromB = Default::default();
 
-        ts.extend(SizeHint(lo, hi, marker::PhantomData));
-        us.extend(SizeHint(lo, hi, marker::PhantomData));
-
         for (t, u) in self {
             ts.extend(Some(t));
             us.extend(Some(u));