diff --git a/src/liballoc/slice.rs b/src/liballoc/slice.rs
index b41cb912fe798..328a26ac5037f 100644
--- a/src/liballoc/slice.rs
+++ b/src/liballoc/slice.rs
@@ -1830,6 +1830,13 @@ impl<T> Borrow<[T]> for Vec<T> {
     }
 }
 
+#[unstable(feature = "borrow_ref_vec", issue = "45808")]
+impl<'a, T> Borrow<[T]> for &'a Vec<T> {
+    fn borrow(&self) -> &[T] {
+        &self[..]
+    }
+}
+
 #[stable(feature = "rust1", since = "1.0.0")]
 impl<T> BorrowMut<[T]> for Vec<T> {
     fn borrow_mut(&mut self) -> &mut [T] {
@@ -1837,6 +1844,20 @@ impl<T> BorrowMut<[T]> for Vec<T> {
     }
 }
 
+#[unstable(feature = "borrow_ref_vec", issue = "45808")]
+impl<'a, T> Borrow<[T]> for &'a mut Vec<T> {
+    fn borrow(&self) -> &[T] {
+        &self[..]
+    }
+}
+
+#[unstable(feature = "borrow_ref_vec", issue = "45808")]
+impl<'a, T> BorrowMut<[T]> for &'a mut Vec<T> {
+    fn borrow_mut(&mut self) -> &mut [T] {
+        &mut self[..]
+    }
+}
+
 #[stable(feature = "rust1", since = "1.0.0")]
 impl<T: Clone> ToOwned for [T] {
     type Owned = Vec<T>;
diff --git a/src/liballoc/str.rs b/src/liballoc/str.rs
index 5f0b4088fc07e..4c13905fb98f9 100644
--- a/src/liballoc/str.rs
+++ b/src/liballoc/str.rs
@@ -47,7 +47,7 @@ use core::iter::FusedIterator;
 use std_unicode::str::{UnicodeStr, Utf16Encoder};
 
 use vec_deque::VecDeque;
-use borrow::{Borrow, ToOwned};
+use borrow::{Borrow, BorrowMut, ToOwned};
 use string::String;
 use std_unicode;
 use vec::Vec;
@@ -182,6 +182,38 @@ impl Borrow<str> for String {
     }
 }
 
+#[unstable(feature = "borrow_mut_string", issue = "45808")]
+impl<'a> BorrowMut<str> for String {
+    #[inline]
+    fn borrow_mut(&mut self) -> &mut str {
+        &mut self[..]
+    }
+}
+
+#[unstable(feature = "borrow_ref_string", issue = "45808")]
+impl<'a> Borrow<str> for &'a String {
+    #[inline]
+    fn borrow(&self) -> &str {
+        &self[..]
+    }
+}
+
+#[unstable(feature = "borrow_ref_string", issue = "45808")]
+impl<'a> Borrow<str> for &'a mut String {
+    #[inline]
+    fn borrow(&self) -> &str {
+        &self[..]
+    }
+}
+
+#[unstable(feature = "borrow_ref_string", issue = "45808")]
+impl<'a> BorrowMut<str> for &'a mut String {
+    #[inline]
+    fn borrow_mut(&mut self) -> &mut str {
+        &mut self[..]
+    }
+}
+
 #[stable(feature = "rust1", since = "1.0.0")]
 impl ToOwned for str {
     type Owned = String;