diff --git a/core/src/muxing.rs b/core/src/muxing.rs
index 0c1b9bffd766..71927b463f3b 100644
--- a/core/src/muxing.rs
+++ b/core/src/muxing.rs
@@ -81,7 +81,7 @@ pub trait StreamMuxer {
     type OutboundSubstream;
 
     /// Error type of the muxer
-    type Error: std::error::Error + Send + Sync + 'static;
+    type Error: std::error::Error;
 
     /// Polls for a connection-wide event.
     ///
diff --git a/core/src/muxing/boxed.rs b/core/src/muxing/boxed.rs
index f53f4d00983e..f22469ded8dc 100644
--- a/core/src/muxing/boxed.rs
+++ b/core/src/muxing/boxed.rs
@@ -39,6 +39,7 @@ impl<T> StreamMuxer for Wrap<T>
 where
     T: StreamMuxer,
     T::Substream: AsyncRead + AsyncWrite + Send + Unpin + 'static,
+    T::Error: Send + Sync + 'static,
 {
     type Substream = SubstreamBox;
     type OutboundSubstream = usize; // TODO: use a newtype
@@ -111,6 +112,7 @@ impl StreamMuxerBox {
         T: StreamMuxer + Send + Sync + 'static,
         T::OutboundSubstream: Send,
         T::Substream: AsyncRead + AsyncWrite + Send + Unpin + 'static,
+        T::Error: Send + Sync + 'static,
     {
         let wrap = Wrap {
             inner: muxer,
diff --git a/core/src/transport/upgrade.rs b/core/src/transport/upgrade.rs
index a20f72129719..281171a01117 100644
--- a/core/src/transport/upgrade.rs
+++ b/core/src/transport/upgrade.rs
@@ -302,6 +302,7 @@ impl<T> Multiplexed<T> {
         M: StreamMuxer + Send + Sync + 'static,
         M::Substream: AsyncRead + AsyncWrite + Send + Unpin + 'static,
         M::OutboundSubstream: Send + 'static,
+        M::Error: Send + Sync + 'static,
     {
         boxed(self.map(|(i, m), _| (i, StreamMuxerBox::new(m))))
     }