diff --git a/src/commands/relay.rs b/src/commands/relay.rs
index c382293..6c5b29b 100644
--- a/src/commands/relay.rs
+++ b/src/commands/relay.rs
@@ -58,9 +58,9 @@ impl RelayServer {
     }
 
     fn post_stream<I: AsRef<[u8]>, S: Stream<Item = I> + 'static>(&self, stream: S) -> BodyStream
-    where S::Error: Error {
+    where S::Error: Error + Send {
         let source = stream
-            .map_err(|err| WebmetroError::Unknown(err.into()))
+            .map_err(|err| WebmetroError::Unknown(Box::new(err)))
             .parse_ebml().chunk_webm();
         let sink = Transmitter::new(self.get_channel());
 
diff --git a/src/error.rs b/src/error.rs
index 2073d53..050f147 100644
--- a/src/error.rs
+++ b/src/error.rs
@@ -14,7 +14,7 @@ use ebml::EbmlError;
 pub enum WebmetroError {
     EbmlError(EbmlError),
     IoError(IoError),
-    Unknown(Box<Error>)
+    Unknown(Box<Error + Send>)
 }
 
 impl Display for WebmetroError {
@@ -48,8 +48,8 @@ impl From<IoError> for WebmetroError {
     }
 }
 
-impl From<Box<Error>> for WebmetroError {
-    fn from(err: Box<Error>) -> WebmetroError {
+impl From<Box<Error + Send>> for WebmetroError {
+    fn from(err: Box<Error + Send>) -> WebmetroError {
         WebmetroError::Unknown(err)
     }
 }