diff --git a/tonic-web/src/call.rs b/tonic-web/src/call.rs
index 98968048a..5e372349e 100644
--- a/tonic-web/src/call.rs
+++ b/tonic-web/src/call.rs
@@ -160,7 +160,8 @@ impl<B> GrpcWebCall<B> {
 
 impl<B> GrpcWebCall<B>
 where
-    B: Body<Data = Bytes>,
+    B: Body,
+    B::Data: Buf,
     B::Error: Error,
 {
     // Poll body for data, decoding (e.g. via Base64 if necessary) and returning frames
@@ -169,7 +170,7 @@ where
     fn poll_decode(
         mut self: Pin<&mut Self>,
         cx: &mut Context<'_>,
-    ) -> Poll<Option<Result<Frame<B::Data>, Status>>> {
+    ) -> Poll<Option<Result<Frame<Bytes>, Status>>> {
         match self.encoding {
             Encoding::Base64 => loop {
                 if let Some(bytes) = self.as_mut().decode_chunk()? {
@@ -179,7 +180,9 @@ where
                 let mut this = self.as_mut().project();
 
                 match ready!(this.inner.as_mut().poll_frame(cx)) {
-                    Some(Ok(frame)) if frame.is_data() => this.buf.put(frame.into_data().unwrap()),
+                    Some(Ok(frame)) if frame.is_data() => this
+                        .buf
+                        .put(frame.into_data().unwrap_or_else(|_| unreachable!())),
                     Some(Ok(frame)) if frame.is_trailers() => {
                         return Poll::Ready(Some(Err(internal_error(
                             "malformed base64 request has unencoded trailers",
@@ -201,19 +204,25 @@ where
                 }
             },
 
-            Encoding::None => self.project().inner.poll_frame(cx).map_err(internal_error),
+            Encoding::None => self
+                .project()
+                .inner
+                .poll_frame(cx)
+                .map_ok(|f| f.map_data(|mut d| d.copy_to_bytes(d.remaining())))
+                .map_err(internal_error),
         }
     }
 
     fn poll_encode(
         mut self: Pin<&mut Self>,
         cx: &mut Context<'_>,
-    ) -> Poll<Option<Result<Frame<B::Data>, Status>>> {
+    ) -> Poll<Option<Result<Frame<Bytes>, Status>>> {
         let mut this = self.as_mut().project();
 
         match ready!(this.inner.as_mut().poll_frame(cx)) {
             Some(Ok(frame)) if frame.is_data() => {
-                let mut res = frame.into_data().unwrap();
+                let mut data = frame.into_data().unwrap_or_else(|_| unreachable!());
+                let mut res = data.copy_to_bytes(data.remaining());
 
                 if *this.encoding == Encoding::Base64 {
                     res = crate::util::base64::STANDARD.encode(res).into();
@@ -222,12 +231,14 @@ where
                 Poll::Ready(Some(Ok(Frame::data(res))))
             }
             Some(Ok(frame)) if frame.is_trailers() => {
-                let trailers = frame.into_trailers().expect("must be trailers");
-                let mut frame = make_trailers_frame(trailers);
+                let trailers = frame.into_trailers().unwrap_or_else(|_| unreachable!());
+                let mut res = make_trailers_frame(trailers);
+
                 if *this.encoding == Encoding::Base64 {
-                    frame = crate::util::base64::STANDARD.encode(frame).into_bytes();
+                    res = crate::util::base64::STANDARD.encode(res).into();
                 }
-                Poll::Ready(Some(Ok(Frame::data(frame.into()))))
+
+                Poll::Ready(Some(Ok(Frame::data(res))))
             }
             Some(Ok(_)) => Poll::Ready(Some(Err(internal_error("unexpected frame type")))),
             Some(Err(e)) => Poll::Ready(Some(Err(internal_error(e)))),
@@ -238,7 +249,7 @@ where
 
 impl<B> Body for GrpcWebCall<B>
 where
-    B: Body<Data = Bytes>,
+    B: Body,
     B::Error: Error,
 {
     type Data = Bytes;
@@ -327,7 +338,7 @@ where
 
 impl<B> Stream for GrpcWebCall<B>
 where
-    B: Body<Data = Bytes>,
+    B: Body,
     B::Error: Error,
 {
     type Item = Result<Frame<Bytes>, Status>;
@@ -430,17 +441,17 @@ fn decode_trailers_frame(mut buf: Bytes) -> Result<Option<HeaderMap>, Status> {
     Ok(Some(map))
 }
 
-fn make_trailers_frame(trailers: HeaderMap) -> Vec<u8> {
+fn make_trailers_frame(trailers: HeaderMap) -> Bytes {
     let trailers = encode_trailers(trailers);
     let len = trailers.len();
     assert!(len <= u32::MAX as usize);
 
-    let mut frame = Vec::with_capacity(len + FRAME_HEADER_SIZE);
-    frame.push(GRPC_WEB_TRAILERS_BIT);
+    let mut frame = BytesMut::with_capacity(len + FRAME_HEADER_SIZE);
+    frame.put_u8(GRPC_WEB_TRAILERS_BIT);
     frame.put_u32(len as u32);
-    frame.extend(trailers);
+    frame.put_slice(&trailers);
 
-    frame
+    frame.freeze()
 }
 
 /// Search some buffer for grpc-web trailers headers and return