diff --git a/src/adaptors.rs b/src/adaptors.rs
index 3d7886e0c..cf2fd3503 100644
--- a/src/adaptors.rs
+++ b/src/adaptors.rs
@@ -287,7 +287,7 @@ impl<I: Iterator> Iterator for Dedup<I> where
     #[inline]
     fn next(&mut self) -> Option<I::Item>
     {
-        for elt in self.iter {
+        for elt in self.iter.by_ref() {
             match self.last {
                 Some(ref x) if x == &elt => continue,
                 None => {
@@ -391,7 +391,7 @@ impl<K: PartialEq, I: Iterator, F: FnMut(&I::Item) -> K>
     type Item = (K, Vec<I::Item>);
     fn next(&mut self) -> Option<(K, Vec<I::Item>)>
     {
-        for elt in self.iter {
+        for elt in self.iter.by_ref() {
             let key = (self.key)(&elt);
             match self.current_key.take() {
                 None => {}
diff --git a/src/lib.rs b/src/lib.rs
index 44347da80..833394319 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -428,9 +428,10 @@ pub trait Itertools : Iterator {
     /// Find the position and value of the first element satisfying a predicate.
     fn find_position<P>(&mut self, mut pred: P) -> Option<(usize, Self::Item)> where
         P: FnMut(&Self::Item) -> bool,
+        Self: Sized,
     {
         let mut index = 0us;
-        for elt in *self {
+        for elt in IteratorExt::by_ref(self) {
             if pred(&elt) {
                 return Some((index, elt))
             }
@@ -477,9 +478,10 @@ pub trait Itertools : Iterator {
     /// "hi".chars().map(|c| cnt += 1).drain();
     /// ```
     ///
-    fn drain(&mut self)
+    fn drain(&mut self) where
+        Self: Sized
     {
-        for _ in *self { /* nothing */ }
+        for _ in self.by_ref() { /* nothing */ }
     }
 
     /// Run the closure **f** eagerly on each element of the iterator.
@@ -487,7 +489,8 @@ pub trait Itertools : Iterator {
     /// Consumes the iterator until its end.
     ///
     /// **Note: This method is deprecated, use .foreach() instead.**
-    fn apply<F: FnMut(Self::Item)>(&mut self, f: F)
+    fn apply<F: FnMut(Self::Item)>(&mut self, f: F) where
+        Self: Sized
     {
         self.foreach(f)
     }
@@ -495,9 +498,10 @@ pub trait Itertools : Iterator {
     /// Run the closure **f** eagerly on each element of the iterator.
     ///
     /// Consumes the iterator until its end.
-    fn foreach<F: FnMut(Self::Item)>(&mut self, mut f: F)
+    fn foreach<F: FnMut(Self::Item)>(&mut self, mut f: F) where
+        Self: Sized
     {
-        for elt in *self { f(elt) }
+        for elt in self.by_ref() { f(elt) }
     }
 
     /// **.collec_vec()** is simply a type specialization of **.collect()**,
@@ -517,7 +521,7 @@ impl<T: ?Sized> Itertools for T where T: Iterator { }
 /// Return the number of elements written.
 #[inline]
 pub fn write<'a, A: 'a, I: Iterator<Item=&'a mut A>, J: Iterator<Item=A>>
-    (mut to: I, mut from: J) -> usize
+    (mut to: I, from: J) -> usize
 {
     let mut count = 0;
     for elt in from {
diff --git a/tests/tests.rs b/tests/tests.rs
index f61a8502e..241c49263 100644
--- a/tests/tests.rs
+++ b/tests/tests.rs
@@ -4,7 +4,7 @@
 //! option. This file may not be copied, modified, or distributed
 //! except according to those terms.
 
-#![feature(core, collections, test)]
+#![feature(core, test)]
 
 #[macro_use]
 extern crate itertools;
@@ -276,20 +276,17 @@ fn rciter() {
 
 #[test]
 fn slice() {
-
-    let it = 0..10;
-    assert_iters_equal(it.slice(..3), 0..3);
-    assert_iters_equal(it.slice(3..7), 3..7);
-    assert_iters_equal(it.slice(3..27), 3..10);
-    assert_iters_equal(it.slice(44..), 0..0);
+    assert_iters_equal((0..10).slice(..3), 0..3);
+    assert_iters_equal((0..10).slice(3..7), 3..7);
+    assert_iters_equal((0..10).slice(3..27), 3..10);
+    assert_iters_equal((0..10).slice(44..), 0..0);
 }
 
 #[test]
 fn step() {
-    let it = 0..10;
-    assert_iters_equal(it.step(1), it);
-    assert_iters_equal(it.step(2), it.filter(|x: &i32| *x % 2 == 0));
-    assert_iters_equal(it.step(10), 0..1);
+    assert_iters_equal((0..10).step(1), (0..10));
+    assert_iters_equal((0..10).step(2), (0..10).filter(|x: &i32| *x % 2 == 0));
+    assert_iters_equal((0..10).step(10), 0..1);
 }
 
 #[test]
diff --git a/tests/zip.rs b/tests/zip.rs
index b93b55c89..1ebcf2c01 100644
--- a/tests/zip.rs
+++ b/tests/zip.rs
@@ -15,11 +15,10 @@ fn test_zip_longest_size_hint() {
     let c = count(0, 1);
     let v: &[_] = &[0, 1, 2, 3, 4, 5, 6, 7, 8, 9];
     let v2 = &[10, 11, 12];
-    let vi = v.iter();
 
-    assert_eq!(c.zip_longest(vi).size_hint(), (std::usize::MAX, None));
+    assert_eq!(c.zip_longest(v.iter()).size_hint(), (std::usize::MAX, None));
 
-    assert_eq!(vi.zip_longest(v2.iter()).size_hint(), (10, Some(10)));
+    assert_eq!(v.iter().zip_longest(v2.iter()).size_hint(), (10, Some(10)));
 }
 #[test]
 fn test_double_ended_zip_longest() {