diff --git a/src/liballoc/arc.rs b/src/liballoc/arc.rs
index dc1938cac1a..ce25f907ec2 100644
--- a/src/liballoc/arc.rs
+++ b/src/liballoc/arc.rs
@@ -265,7 +265,7 @@ impl<T> Deref for Arc<T> {
     }
 }
 
-impl<T: Send + Sync + Clone> Arc<T> {
+impl<T: Clone> Arc<T> {
     /// Make a mutable reference from the given `Arc<T>`.
     ///
     /// This is also referred to as a copy-on-write operation because the inner data is cloned if
@@ -300,7 +300,7 @@ impl<T: Send + Sync + Clone> Arc<T> {
 
 #[unsafe_destructor]
 #[stable(feature = "rust1", since = "1.0.0")]
-impl<T: Sync + Send> Drop for Arc<T> {
+impl<T> Drop for Arc<T> {
     /// Drops the `Arc<T>`.
     ///
     /// This will decrement the strong reference count. If the strong reference count becomes zero
@@ -367,7 +367,7 @@ impl<T: Sync + Send> Drop for Arc<T> {
 
 #[unstable(feature = "alloc",
            reason = "Weak pointers may not belong in this module.")]
-impl<T: Sync + Send> Weak<T> {
+impl<T> Weak<T> {
     /// Upgrades a weak reference to a strong reference.
     ///
     /// Upgrades the `Weak<T>` reference to an `Arc<T>`, if possible.
@@ -406,7 +406,7 @@ impl<T: Sync + Send> Weak<T> {
 
 #[unstable(feature = "alloc",
            reason = "Weak pointers may not belong in this module.")]
-impl<T: Sync + Send> Clone for Weak<T> {
+impl<T> Clone for Weak<T> {
     /// Makes a clone of the `Weak<T>`.
     ///
     /// This increases the weak reference count.
@@ -430,7 +430,7 @@ impl<T: Sync + Send> Clone for Weak<T> {
 
 #[unsafe_destructor]
 #[stable(feature = "rust1", since = "1.0.0")]
-impl<T: Sync + Send> Drop for Weak<T> {
+impl<T> Drop for Weak<T> {
     /// Drops the `Weak<T>`.
     ///
     /// This will decrement the weak reference count.