diff --git a/src/liballoc/slice.rs b/src/liballoc/slice.rs
index d24d292a1ec9a..da6254092382d 100644
--- a/src/liballoc/slice.rs
+++ b/src/liballoc/slice.rs
@@ -981,7 +981,7 @@ impl<T> [T] {
     /// ```
     #[stable(feature = "rust1", since = "1.0.0")]
     pub fn contains<U>(&self, x: &U) -> bool
-        where T: PartialEq<U>
+        where U: ?Sized, T: PartialEq<U>
     {
         core_slice::SliceExt::contains(self, x)
     }
diff --git a/src/liballoc/tests/slice.rs b/src/liballoc/tests/slice.rs
index 6afff7ef9182a..d1642b1cdc75f 100644
--- a/src/liballoc/tests/slice.rs
+++ b/src/liballoc/tests/slice.rs
@@ -1062,6 +1062,7 @@ fn test_contains() {
     assert!(!strings.contains(&String::from("A")));
     assert!(strings.contains(&"AB"));
     assert!(!strings.contains(&"BC"));
+    assert!(strings.contains("AB"));
 }
 
 #[test]
diff --git a/src/libcore/slice/mod.rs b/src/libcore/slice/mod.rs
index e2a4e37252481..963923dbeddf9 100644
--- a/src/libcore/slice/mod.rs
+++ b/src/libcore/slice/mod.rs
@@ -192,7 +192,7 @@ pub trait SliceExt {
     fn as_mut_ptr(&mut self) -> *mut Self::Item;
 
     #[stable(feature = "core", since = "1.6.0")]
-    fn contains<U>(&self, x: &U) -> bool where Self::Item: PartialEq<U>;
+    fn contains<U>(&self, x: &U) -> bool where U: ?Sized, Self::Item: PartialEq<U>;
 
     #[stable(feature = "core", since = "1.6.0")]
     fn starts_with(&self, needle: &[Self::Item]) -> bool where Self::Item: PartialEq;
@@ -618,7 +618,7 @@ impl<T> SliceExt for [T] {
     }
 
     #[inline]
-    fn contains<U>(&self, x: &U) -> bool where T: PartialEq<U> {
+    fn contains<U>(&self, x: &U) -> bool where U: ?Sized, T: PartialEq<U> {
         self.iter().any(|e| e == x)
     }