diff --git a/Cargo.lock b/Cargo.lock
index e5d2d394..6f24acf0 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -3572,7 +3572,7 @@ dependencies = [
 
 [[package]]
 name = "wit-bindgen-wrpc"
-version = "0.4.4"
+version = "0.4.5"
 dependencies = [
  "anyhow",
  "bitflags 2.6.0",
@@ -3600,7 +3600,7 @@ dependencies = [
 
 [[package]]
 name = "wit-bindgen-wrpc-rust"
-version = "0.4.4"
+version = "0.4.5"
 dependencies = [
  "anyhow",
  "clap",
@@ -3616,7 +3616,7 @@ dependencies = [
 
 [[package]]
 name = "wit-bindgen-wrpc-rust-macro"
-version = "0.4.4"
+version = "0.4.5"
 dependencies = [
  "anyhow",
  "prettyplease",
@@ -3748,7 +3748,7 @@ dependencies = [
 
 [[package]]
 name = "wrpc-transport"
-version = "0.26.2"
+version = "0.26.3"
 dependencies = [
  "anyhow",
  "bytes",
diff --git a/Cargo.toml b/Cargo.toml
index a0f5c810..44d254f8 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -128,16 +128,16 @@ wasmtime = { version = "22", default-features = false }
 wasmtime-wasi = { version = "22", default-features = false }
 wit-bindgen = { version = "0.27", default-features = false }
 wit-bindgen-core = { version = "0.27", default-features = false }
-wit-bindgen-wrpc = { version = "0.4.4", default-features = false, path = "./crates/wit-bindgen" }
+wit-bindgen-wrpc = { version = "0.4.5", default-features = false, path = "./crates/wit-bindgen" }
 wit-bindgen-wrpc-go = { version = "0.2", default-features = false, path = "./crates/wit-bindgen-go" }
-wit-bindgen-wrpc-rust = { version = "0.4.4", default-features = false, path = "./crates/wit-bindgen-rust" }
-wit-bindgen-wrpc-rust-macro = { version = "0.4.4", default-features = false, path = "./crates/wit-bindgen-rust-macro" }
+wit-bindgen-wrpc-rust = { version = "0.4.5", default-features = false, path = "./crates/wit-bindgen-rust" }
+wit-bindgen-wrpc-rust-macro = { version = "0.4.5", default-features = false, path = "./crates/wit-bindgen-rust-macro" }
 wit-component = { version = "0.212", default-features = false }
 wit-parser = { version = "0.212", default-features = false }
 wrpc-cli = { version = "0.2", path = "./crates/cli", default-features = false }
 wrpc-introspect = { version = "0.1", default-features = false, path = "./crates/introspect" }
 wrpc-runtime-wasmtime = { version = "0.19", path = "./crates/runtime-wasmtime", default-features = false }
-wrpc-transport = { version = "0.26", path = "./crates/transport", default-features = false }
+wrpc-transport = { version = "0.26.3", path = "./crates/transport", default-features = false }
 wrpc-transport-nats = { version = "0.22", path = "./crates/transport-nats", default-features = false }
 wrpc-transport-quic = { version = "0.1", path = "./crates/transport-quic", default-features = false }
 wrpc-wasmtime-nats-cli = { version = "0.3", path = "./crates/wasmtime-nats-cli", default-features = false }
diff --git a/crates/transport/Cargo.toml b/crates/transport/Cargo.toml
index 730e0b69..2795a8f8 100644
--- a/crates/transport/Cargo.toml
+++ b/crates/transport/Cargo.toml
@@ -1,6 +1,6 @@
 [package]
 name = "wrpc-transport"
-version = "0.26.2"
+version = "0.26.3"
 description = "wRPC core transport functionality"
 
 authors.workspace = true
diff --git a/crates/transport/src/lib.rs b/crates/transport/src/lib.rs
index d9a42fcc..f698822a 100644
--- a/crates/transport/src/lib.rs
+++ b/crates/transport/src/lib.rs
@@ -282,21 +282,16 @@ pub trait Serve: Sync {
                     Item = anyhow::Result<(
                         Self::Context,
                         Params,
-                        Option<
-                            impl Future<Output = std::io::Result<()>> + Sync + Send + Unpin + 'static,
-                        >,
-                        impl FnOnce(
-                            Results,
-                        )
-                            -> Pin<Box<dyn Future<Output = anyhow::Result<()>> + Sync + Send>>,
+                        Option<impl Future<Output = std::io::Result<()>> + Send + Unpin + 'static>,
+                        impl FnOnce(Results) -> Pin<Box<dyn Future<Output = anyhow::Result<()>> + Send>>,
                     )>,
                 > + Send
                 + 'static,
         >,
     > + Send
     where
-        Params: TupleDecode<Self::Incoming> + Send + Sync + 'static,
-        Results: TupleEncode<Self::Outgoing> + Send + Sync + 'static,
+        Params: TupleDecode<Self::Incoming> + Send + 'static,
+        Results: TupleEncode<Self::Outgoing> + Send + 'static,
         <Params::Decoder as tokio_util::codec::Decoder>::Error:
             std::error::Error + Send + Sync + 'static,
         <Results::Encoder as tokio_util::codec::Encoder<Results>>::Error:
@@ -368,13 +363,7 @@ mod tests {
     #[allow(clippy::manual_async_fn)]
     fn invoke_values_send<T>() -> impl Future<
         Output = anyhow::Result<(
-            Pin<
-                Box<
-                    dyn Stream<Item = Vec<Pin<Box<dyn Future<Output = String> + Send + Sync>>>>
-                        + Send
-                        + Sync,
-                >,
-            >,
+            Pin<Box<dyn Stream<Item = Vec<Pin<Box<dyn Future<Output = String> + Send>>>> + Send>>,
         )>,
     > + Send
     where
@@ -404,8 +393,7 @@ mod tests {
         i.invoke(cx, "foo", "bar", Bytes::default(), &paths).await
     }
 
-    async fn call_invoke_async<T>(
-    ) -> anyhow::Result<(Pin<Box<dyn Stream<Item = Bytes> + Send + Sync>>,)>
+    async fn call_invoke_async<T>() -> anyhow::Result<(Pin<Box<dyn Stream<Item = Bytes> + Send>>,)>
     where
         T: Invoke<Context = ()> + Default,
     {
diff --git a/crates/transport/src/value.rs b/crates/transport/src/value.rs
index 2459c9a3..d41c1c12 100644
--- a/crates/transport/src/value.rs
+++ b/crates/transport/src/value.rs
@@ -156,12 +156,8 @@ impl<T: ?Sized> ResourceOwn<T> {
 }
 
 pub type DeferredFn<T> = Box<
-    dyn FnOnce(
-            Arc<T>,
-            Vec<usize>,
-        ) -> Pin<Box<dyn Future<Output = std::io::Result<()>> + Send + Sync>>
-        + Send
-        + Sync,
+    dyn FnOnce(Arc<T>, Vec<usize>) -> Pin<Box<dyn Future<Output = std::io::Result<()>> + Send>>
+        + Send,
 >;
 
 pub trait Deferred<T> {
@@ -325,7 +321,7 @@ where
 }
 
 pub trait Encode<T>: Sized {
-    type Encoder: tokio_util::codec::Encoder<Self> + Deferred<T> + Default + Send + Sync;
+    type Encoder: tokio_util::codec::Encoder<Self> + Deferred<T> + Default + Send;
 
     #[instrument(level = "trace", skip(self, enc))]
     fn encode(
@@ -752,9 +748,9 @@ where
 
 impl<T, R> Decode<R> for Vec<T>
 where
-    T: Decode<R> + Send + Sync,
+    T: Decode<R> + Send,
     T::ListDecoder: Deferred<R> + Send,
-    R: crate::Index<R> + Send + Sync + 'static,
+    R: crate::Index<R> + Send + 'static,
 {
     type Decoder = T::ListDecoder;
     type ListDecoder = ListDecoder<Self::Decoder, R>;
@@ -1119,7 +1115,7 @@ impl<R, T: ?Sized> Deferred<R> for CoreVecDecoder<ResourceBorrowDecoder<T>> {
     }
 }
 
-impl<R, T: ?Sized + Send + Sync + 'static> Decode<R> for ResourceBorrow<T> {
+impl<R, T: ?Sized + Send + 'static> Decode<R> for ResourceBorrow<T> {
     type Decoder = ResourceBorrowDecoder<T>;
     type ListDecoder = CoreVecDecoder<Self::Decoder>;
 }
@@ -1163,7 +1159,7 @@ impl<R, T: ?Sized> Deferred<R> for CoreVecDecoder<ResourceOwnDecoder<T>> {
     }
 }
 
-impl<R, T: ?Sized + Send + Sync + 'static> Decode<R> for ResourceOwn<T> {
+impl<R, T: ?Sized + Send + 'static> Decode<R> for ResourceOwn<T> {
     type Decoder = ResourceOwnDecoder<T>;
     type ListDecoder = CoreVecDecoder<Self::Decoder>;
 }
@@ -1304,8 +1300,8 @@ macro_rules! impl_tuple_codec {
             R: crate::Index<R> + Send + Sync + 'static,
             E: From<std::io::Error>,
             $(
-                $vt: Decode<R> + Send + Sync + 'static,
-                $vt::Decoder: tokio_util::codec::Decoder<Error = E> + Send + Sync + 'static,
+                $vt: Decode<R> + Send + 'static,
+                $vt::Decoder: tokio_util::codec::Decoder<Error = E> + Send + 'static,
             )+
         {
             type Decoder = TupleDecoder::<($($vt::Decoder),+,), ($(Option<$vt>),+,)>;
@@ -1317,8 +1313,8 @@ macro_rules! impl_tuple_codec {
             R: crate::Index<R> + Send + Sync + 'static,
             E: From<std::io::Error>,
             $(
-                $vt: Decode<R> + Send + Sync + 'static,
-                $vt::Decoder: tokio_util::codec::Decoder<Error = E> + Send + Sync + 'static,
+                $vt: Decode<R> + Send + 'static,
+                $vt::Decoder: tokio_util::codec::Decoder<Error = E> + Send + 'static,
             )+
         {
         }
@@ -1457,7 +1453,7 @@ impl<T, W, Fut> tokio_util::codec::Encoder<Fut> for FutureEncoder<W>
 where
     T: Encode<W>,
     W: AsyncWrite + crate::Index<W> + Send + Sync + Unpin + 'static,
-    Fut: Future<Output = T> + Send + Sync + 'static,
+    Fut: Future<Output = T> + Send + 'static,
     std::io::Error: From<<T::Encoder as tokio_util::codec::Encoder<T>>::Error>,
 {
     type Error = std::io::Error;
@@ -1489,7 +1485,7 @@ where
     }
 }
 
-impl<T, W> Encode<W> for Pin<Box<dyn Future<Output = T> + Send + Sync>>
+impl<T, W> Encode<W> for Pin<Box<dyn Future<Output = T> + Send>>
 where
     T: Encode<W> + 'static,
     W: AsyncWrite + crate::Index<W> + Send + Sync + Unpin + 'static,
@@ -1531,12 +1527,11 @@ where
 
 impl<T, R> tokio_util::codec::Decoder for FutureDecoder<T, R>
 where
-    T: Decode<R> + Send + Sync + 'static,
-    T::Decoder: Sync,
+    T: Decode<R> + Send + 'static,
     R: AsyncRead + crate::Index<R> + Send + Sync + Unpin + 'static,
     std::io::Error: From<<T::Decoder as tokio_util::codec::Decoder>::Error>,
 {
-    type Item = Pin<Box<dyn Future<Output = T> + Send + Sync>>;
+    type Item = Pin<Box<dyn Future<Output = T> + Send>>;
     type Error = <T::Decoder as tokio_util::codec::Decoder>::Error;
 
     #[instrument(level = "trace", skip(self), fields(ty = "future"))]
@@ -1588,10 +1583,9 @@ where
     }
 }
 
-impl<T, R> Decode<R> for Pin<Box<dyn Future<Output = T> + Send + Sync>>
+impl<T, R> Decode<R> for Pin<Box<dyn Future<Output = T> + Send>>
 where
-    T: Decode<R> + Send + Sync + 'static,
-    T::Decoder: Sync,
+    T: Decode<R> + Send + 'static,
     R: AsyncRead + crate::Index<R> + Send + Sync + Unpin + 'static,
     std::io::Error: From<<T::Decoder as tokio_util::codec::Decoder>::Error>,
 {
@@ -1617,9 +1611,9 @@ impl<W> Deferred<W> for StreamEncoder<W> {
 
 impl<T, W, S> tokio_util::codec::Encoder<S> for StreamEncoder<W>
 where
-    T: Encode<W> + Send + Sync + 'static,
+    T: Encode<W> + Send + 'static,
     W: AsyncWrite + crate::Index<W> + Send + Sync + Unpin + 'static,
-    S: Stream<Item = Vec<T>> + Send + Sync + Unpin + 'static,
+    S: Stream<Item = Vec<T>> + Send + Unpin + 'static,
     std::io::Error: From<<T::Encoder as tokio_util::codec::Encoder<T>>::Error>,
 {
     type Error = std::io::Error;
@@ -1689,9 +1683,9 @@ where
     }
 }
 
-impl<T, W> Encode<W> for Pin<Box<dyn Stream<Item = Vec<T>> + Send + Sync>>
+impl<T, W> Encode<W> for Pin<Box<dyn Stream<Item = Vec<T>> + Send>>
 where
-    T: Encode<W> + Send + Sync + 'static,
+    T: Encode<W> + Send + 'static,
     W: AsyncWrite + crate::Index<W> + Send + Sync + Unpin + 'static,
     std::io::Error: From<<T::Encoder as tokio_util::codec::Encoder<T>>::Error>,
 {
@@ -1717,7 +1711,7 @@ impl<W> Deferred<W> for StreamEncoderBytes<W> {
 impl<W, S> tokio_util::codec::Encoder<S> for StreamEncoderBytes<W>
 where
     W: AsyncWrite + crate::Index<W> + Send + Sync + Unpin + 'static,
-    S: Stream<Item = Bytes> + Send + Sync + Unpin + 'static,
+    S: Stream<Item = Bytes> + Send + Unpin + 'static,
 {
     type Error = std::io::Error;
 
@@ -1758,7 +1752,7 @@ where
     }
 }
 
-impl<W> Encode<W> for Pin<Box<dyn Stream<Item = Bytes> + Send + Sync>>
+impl<W> Encode<W> for Pin<Box<dyn Stream<Item = Bytes> + Send>>
 where
     W: AsyncWrite + crate::Index<W> + Send + Sync + Unpin + 'static,
 {
@@ -1784,7 +1778,7 @@ impl<W> Deferred<W> for StreamEncoderRead<W> {
 impl<W, S> tokio_util::codec::Encoder<S> for StreamEncoderRead<W>
 where
     W: AsyncWrite + crate::Index<W> + Send + Sync + Unpin + 'static,
-    S: AsyncRead + Send + Sync + Unpin + 'static,
+    S: AsyncRead + Send + Unpin + 'static,
 {
     type Error = std::io::Error;
 
@@ -1828,7 +1822,7 @@ where
     }
 }
 
-impl<W> Encode<W> for Pin<Box<dyn AsyncRead + Send + Sync>>
+impl<W> Encode<W> for Pin<Box<dyn AsyncRead + Send>>
 where
     W: AsyncWrite + crate::Index<W> + Send + Sync + Unpin + 'static,
 {
@@ -1837,7 +1831,7 @@ where
 
 impl<T, W> Encode<W> for std::io::Cursor<T>
 where
-    T: AsRef<[u8]> + Send + Sync + Unpin + 'static,
+    T: AsRef<[u8]> + Send + Unpin + 'static,
     W: AsyncWrite + crate::Index<W> + Send + Sync + Unpin + 'static,
 {
     type Encoder = StreamEncoderRead<W>;
@@ -1930,7 +1924,7 @@ async fn handle_deferred_stream<C, T, R>(
 ) -> std::io::Result<()>
 where
     C: tokio_util::codec::Decoder<Item = T> + Deferred<R>,
-    R: AsyncRead + crate::Index<R> + Send + Sync + Unpin + 'static,
+    R: AsyncRead + crate::Index<R> + Send + Unpin + 'static,
     std::io::Error: From<C::Error>,
 {
     let dec = ListDecoder::new(dec);
@@ -1982,14 +1976,13 @@ where
 
 impl<T, R> tokio_util::codec::Decoder for StreamDecoder<T, R>
 where
-    T: Decode<R> + Send + Sync + 'static,
-    T::Decoder: Sync,
+    T: Decode<R> + Send + 'static,
     T::ListDecoder: Deferred<R>,
     R: AsyncRead + crate::Index<R> + Send + Sync + Unpin + 'static,
-    <T::Decoder as tokio_util::codec::Decoder>::Error: Send + Sync,
+    <T::Decoder as tokio_util::codec::Decoder>::Error: Send,
     std::io::Error: From<<T::Decoder as tokio_util::codec::Decoder>::Error>,
 {
-    type Item = Pin<Box<dyn Stream<Item = Vec<T>> + Send + Sync>>;
+    type Item = Pin<Box<dyn Stream<Item = Vec<T>> + Send>>;
     type Error = <<T as Decode<R>>::ListDecoder as tokio_util::codec::Decoder>::Error;
 
     #[instrument(level = "trace", skip(self), fields(ty = "stream"))]
@@ -2013,13 +2006,12 @@ where
     }
 }
 
-impl<T, R> Decode<R> for Pin<Box<dyn Stream<Item = Vec<T>> + Send + Sync>>
+impl<T, R> Decode<R> for Pin<Box<dyn Stream<Item = Vec<T>> + Send>>
 where
-    T: Decode<R> + Send + Sync + 'static,
-    T::Decoder: Sync,
+    T: Decode<R> + Send + 'static,
     T::ListDecoder: Deferred<R> + Send,
     R: AsyncRead + crate::Index<R> + Send + Sync + Unpin + 'static,
-    <T::Decoder as tokio_util::codec::Decoder>::Error: Send + Sync,
+    <T::Decoder as tokio_util::codec::Decoder>::Error: Send,
     std::io::Error: From<<T::Decoder as tokio_util::codec::Decoder>::Error>,
 {
     type Decoder = StreamDecoder<T, R>;
@@ -2050,7 +2042,7 @@ impl<R> tokio_util::codec::Decoder for StreamDecoderBytes<R>
 where
     R: AsyncRead + crate::Index<R> + Send + Sync + Unpin + 'static,
 {
-    type Item = Pin<Box<dyn Stream<Item = Bytes> + Send + Sync>>;
+    type Item = Pin<Box<dyn Stream<Item = Bytes> + Send>>;
     type Error = std::io::Error;
 
     #[instrument(level = "trace", skip(self), fields(ty = "stream<u8>"))]
@@ -2091,7 +2083,7 @@ where
     }
 }
 
-impl<R> Decode<R> for Pin<Box<dyn Stream<Item = Bytes> + Send + Sync>>
+impl<R> Decode<R> for Pin<Box<dyn Stream<Item = Bytes> + Send>>
 where
     R: AsyncRead + crate::Index<R> + Send + Sync + Unpin + 'static,
 {
@@ -2123,7 +2115,7 @@ impl<R> tokio_util::codec::Decoder for StreamDecoderRead<R>
 where
     R: AsyncRead + crate::Index<R> + Send + Sync + Unpin + 'static,
 {
-    type Item = Pin<Box<dyn AsyncRead + Send + Sync>>;
+    type Item = Pin<Box<dyn AsyncRead + Send>>;
     type Error = std::io::Error;
 
     #[instrument(level = "trace", skip(self), fields(ty = "stream<u8>"))]
@@ -2164,7 +2156,7 @@ where
     }
 }
 
-impl<R> Decode<R> for Pin<Box<dyn AsyncRead + Send + Sync>>
+impl<R> Decode<R> for Pin<Box<dyn AsyncRead + Send>>
 where
     R: AsyncRead + crate::Index<R> + Send + Sync + Unpin + 'static,
 {
diff --git a/crates/wit-bindgen-rust-macro/Cargo.toml b/crates/wit-bindgen-rust-macro/Cargo.toml
index 892ef288..1fd7441b 100644
--- a/crates/wit-bindgen-rust-macro/Cargo.toml
+++ b/crates/wit-bindgen-rust-macro/Cargo.toml
@@ -1,6 +1,6 @@
 [package]
 name = "wit-bindgen-wrpc-rust-macro"
-version = "0.4.4"
+version = "0.4.5"
 description = """
 Procedural macro paired with the `wit-bindgen-wrpc` crate.
 """
diff --git a/crates/wit-bindgen-rust/Cargo.toml b/crates/wit-bindgen-rust/Cargo.toml
index 06c69daa..a27ace3c 100644
--- a/crates/wit-bindgen-rust/Cargo.toml
+++ b/crates/wit-bindgen-rust/Cargo.toml
@@ -1,6 +1,6 @@
 [package]
 name = "wit-bindgen-wrpc-rust"
-version = "0.4.4"
+version = "0.4.5"
 description = """
 Rust bindings generator for wRPC, typically used through
 the `wit-bindgen-wrpc` crate's `generate!` macro.
diff --git a/crates/wit-bindgen-rust/src/interface.rs b/crates/wit-bindgen-rust/src/interface.rs
index c99da9b5..efc2a33d 100644
--- a/crates/wit-bindgen-rust/src/interface.rs
+++ b/crates/wit-bindgen-rust/src/interface.rs
@@ -935,7 +935,7 @@ pub async fn serve_interface<T: {wrpc_transport}::Serve, U>(
         } else {
             self.push_str("()");
         }
-        self.push_str("> + ::core::marker::Send + ::core::marker::Sync>>");
+        self.push_str("> + ::core::marker::Send>>");
     }
 
     fn print_stream(&mut self, Stream { element, .. }: &Stream, submodule: bool) {
@@ -949,7 +949,7 @@ pub async fn serve_interface<T: {wrpc_transport}::Serve, U>(
         } else {
             self.push_str("Vec<()>");
         }
-        self.push_str("> + ::core::marker::Send + ::core::marker::Sync>>");
+        self.push_str("> + ::core::marker::Send>>");
     }
 
     fn print_own(&mut self, id: TypeId, submodule: bool) {
diff --git a/crates/wit-bindgen/Cargo.toml b/crates/wit-bindgen/Cargo.toml
index 9fbfb1d5..431bdf11 100644
--- a/crates/wit-bindgen/Cargo.toml
+++ b/crates/wit-bindgen/Cargo.toml
@@ -1,6 +1,6 @@
 [package]
 name = "wit-bindgen-wrpc"
-version = "0.4.4"
+version = "0.4.5"
 description = """
 Rust bindings generator for wRPC.
 """
diff --git a/tests/rust.rs b/tests/rust.rs
index 7246adda..cb775fa9 100644
--- a/tests/rust.rs
+++ b/tests/rust.rs
@@ -234,8 +234,8 @@ where
                     &self,
                     _cx: C,
                 ) -> anyhow::Result<(
-                    Pin<Box<dyn Stream<Item = Bytes> + Send + Sync>>,
-                    Pin<Box<dyn Stream<Item = Vec<Vec<String>>> + Send + Sync>>,
+                    Pin<Box<dyn Stream<Item = Bytes> + Send>>,
+                    Pin<Box<dyn Stream<Item = Vec<Vec<String>>> + Send>>,
                 )> {
                     Ok((
                         Box::pin(stream::iter([Bytes::from("test")])),
@@ -249,15 +249,9 @@ where
                 async fn with_future(
                     &self,
                     _cx: C,
-                    s: Pin<Box<dyn Stream<Item = Bytes> + Send + Sync>>,
+                    s: Pin<Box<dyn Stream<Item = Bytes> + Send>>,
                 ) -> anyhow::Result<
-                    Pin<
-                        Box<
-                            dyn Future<Output = Pin<Box<dyn Stream<Item = Bytes> + Send + Sync>>>
-                                + Send
-                                + Sync,
-                        >,
-                    >,
+                    Pin<Box<dyn Future<Output = Pin<Box<dyn Stream<Item = Bytes> + Send>>> + Send>>,
                 > {
                     Ok(Box::pin(async { s }))
                 }
@@ -687,10 +681,10 @@ where
                 .expect("failed to accept invocation")
                 .expect("unexpected end of stream");
             let (a, b, mut c, d): (
-                Pin<Box<dyn Stream<Item = Vec<u32>> + Send + Sync>>,
-                Pin<Box<dyn Stream<Item = Vec<String>> + Send + Sync>>,
-                Pin<Box<dyn AsyncRead + Send + Sync>>,
-                Pin<Box<dyn Future<Output = Vec<u64>> + Send + Sync>>,
+                Pin<Box<dyn Stream<Item = Vec<u32>> + Send>>,
+                Pin<Box<dyn Stream<Item = Vec<String>> + Send>>,
+                Pin<Box<dyn AsyncRead + Send>>,
+                Pin<Box<dyn Future<Output = Vec<u64>> + Send>>,
             ) = params;
             let io = rx.map(Instrument::in_current_span).map(spawn);
             join!(
@@ -721,25 +715,25 @@ where
                     }
                 }
             );
-            let a: Pin<Box<dyn Stream<Item = Vec<u32>> + Send + Sync>> =
+            let a: Pin<Box<dyn Stream<Item = Vec<u32>> + Send>> =
                 Box::pin(stream::iter([vec![0xc0, 0xff], vec![0xee]]));
 
-            let b: Pin<Box<dyn Stream<Item = Vec<&str>> + Send + Sync>> =
+            let b: Pin<Box<dyn Stream<Item = Vec<&str>> + Send>> =
                 Box::pin(stream::iter([vec!["foo"], vec!["bar"]]));
-            let c: Pin<Box<dyn AsyncRead + Send + Sync>> = Box::pin(b"test".as_slice());
-            let d: Pin<Box<dyn Future<Output = Vec<u64>> + Send + Sync>> =
+            let c: Pin<Box<dyn AsyncRead + Send>> = Box::pin(b"test".as_slice());
+            let d: Pin<Box<dyn Future<Output = Vec<u64>> + Send>> =
                 Box::pin(async { vec![1, 2, 3] });
             info!("transmitting `test.async` returns");
             tx((a, b, c, d)).await.expect("failed to send response");
         }
         .instrument(info_span!("server")),
         async {
-            let a: Pin<Box<dyn Stream<Item = Vec<u32>> + Send + Sync>> =
+            let a: Pin<Box<dyn Stream<Item = Vec<u32>> + Send>> =
                 Box::pin(stream::iter([vec![0xc0, 0xff, 0xee]]));
-            let b: Pin<Box<dyn Stream<Item = Vec<&str>> + Send + Sync>> =
+            let b: Pin<Box<dyn Stream<Item = Vec<&str>> + Send>> =
                 Box::pin(stream::iter([vec!["foo", "bar"]]));
-            let c: Pin<Box<dyn AsyncRead + Send + Sync>> = Box::pin(b"test".as_slice());
-            let d: Pin<Box<dyn Future<Output = Vec<u64>> + Send + Sync>> =
+            let c: Pin<Box<dyn AsyncRead + Send>> = Box::pin(b"test".as_slice());
+            let d: Pin<Box<dyn Future<Output = Vec<u64>> + Send>> =
                 Box::pin(async { vec![1, 2, 3] });
             info!("invoking `test.async`");
             let (returns, io) = clt
@@ -753,10 +747,10 @@ where
                 .await
                 .expect("failed to invoke `test.async`");
             let (a, b, mut c, d): (
-                Pin<Box<dyn Stream<Item = Vec<u32>> + Send + Sync>>,
-                Pin<Box<dyn Stream<Item = Vec<String>> + Send + Sync>>,
-                Pin<Box<dyn AsyncRead + Send + Sync>>,
-                Pin<Box<dyn Future<Output = Vec<u64>> + Send + Sync>>,
+                Pin<Box<dyn Stream<Item = Vec<u32>> + Send>>,
+                Pin<Box<dyn Stream<Item = Vec<String>> + Send>>,
+                Pin<Box<dyn AsyncRead + Send>>,
+                Pin<Box<dyn Future<Output = Vec<u64>> + Send>>,
             ) = returns;
             info!("receiving `test.async` async values");
             join!(