diff --git a/src/libstd/sys/common/poison.rs b/src/libstd/sys/common/poison.rs
index 2cfa04c843b6b..d858c0027558c 100644
--- a/src/libstd/sys/common/poison.rs
+++ b/src/libstd/sys/common/poison.rs
@@ -111,7 +111,7 @@ impl<T> fmt::Display for PoisonError<T> {
 }
 
 #[stable(feature = "rust1", since = "1.0.0")]
-impl<T: Send + Reflect> Error for PoisonError<T> {
+impl<T: Reflect> Error for PoisonError<T> {
     fn description(&self) -> &str {
         "poisoned lock: another task failed inside"
     }
@@ -158,14 +158,17 @@ impl<T> fmt::Debug for TryLockError<T> {
 }
 
 #[stable(feature = "rust1", since = "1.0.0")]
-impl<T: Send + Reflect> fmt::Display for TryLockError<T> {
+impl<T> fmt::Display for TryLockError<T> {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
-        self.description().fmt(f)
+        match *self {
+            TryLockError::Poisoned(..) => "poisoned lock: another task failed inside",
+            TryLockError::WouldBlock => "try_lock failed because the operation would block"
+        }.fmt(f)
     }
 }
 
 #[stable(feature = "rust1", since = "1.0.0")]
-impl<T: Send + Reflect> Error for TryLockError<T> {
+impl<T: Reflect> Error for TryLockError<T> {
     fn description(&self) -> &str {
         match *self {
             TryLockError::Poisoned(ref p) => p.description(),