diff --git a/src/proto/h1/encode.rs b/src/proto/h1/encode.rs
index 2df0c396b7..3be367f8fc 100644
--- a/src/proto/h1/encode.rs
+++ b/src/proto/h1/encode.rs
@@ -179,7 +179,7 @@ impl Encoder {
                     }
                     let name = cur_name.as_ref().expect("current header name");
 
-                    if allowed_trailer_field_map.contains_key(name.as_str()) {
+                    if allowed_trailer_field_map.contains_key(name) {
                         if is_valid_trailer_field(name) {
                             allowed_trailers.insert(name, value);
                         } else {
@@ -279,15 +279,18 @@ fn is_valid_trailer_field(name: &HeaderName) -> bool {
     )
 }
 
-fn allowed_trailer_field_map(allowed_trailer_fields: &Vec<HeaderValue>) -> HashMap<String, ()> {
+fn allowed_trailer_field_map(allowed_trailer_fields: &Vec<HeaderValue>) -> HashMap<HeaderName, ()> {
     let mut trailer_map = HashMap::new();
 
     for header_value in allowed_trailer_fields {
         if let Ok(header_str) = header_value.to_str() {
             let items: Vec<&str> = header_str.split(',').map(|item| item.trim()).collect();
 
-            for item in items {
-                trailer_map.entry(item.to_string()).or_insert(());
+            for item in items
+                .into_iter()
+                .filter_map(|v| HeaderName::from_bytes(v.as_bytes()).ok())
+            {
+                trailer_map.entry(item).or_insert(());
             }
         }
     }
diff --git a/tests/client.rs b/tests/client.rs
index d5a0e4e005..5f976b1792 100644
--- a/tests/client.rs
+++ b/tests/client.rs
@@ -704,6 +704,44 @@ test! {
             body: None,
 }
 
+test! {
+    name: client_post_req_body_chunked_with_trailer_titlecase,
+
+    server:
+        expected: "\
+            POST / HTTP/1.1\r\n\
+            trailer: Chunky-Trailer\r\n\
+            host: {addr}\r\n\
+            transfer-encoding: chunked\r\n\
+            \r\n\
+            5\r\n\
+            hello\r\n\
+            0\r\n\
+            chunky-trailer: header data\r\n\
+            \r\n\
+            ",
+        reply: REPLY_OK,
+
+    client:
+        request: {
+            method: POST,
+            url: "http://{addr}/",
+            headers: {
+                "trailer" => "Chunky-Trailer",
+            },
+            body_stream_with_trailers: (
+                (futures_util::stream::once(async { Ok::<_, Infallible>(Bytes::from("hello"))})),
+                HeaderMap::from_iter(vec![(
+                    HeaderName::from_static("chunky-trailer"),
+                    HeaderValue::from_static("header data")
+                )].into_iter())),
+        },
+        response:
+            status: OK,
+            headers: {},
+            body: None,
+}
+
 test! {
     name: client_res_body_chunked_with_trailer,
 
@@ -740,6 +778,42 @@ test! {
             },
 }
 
+test! {
+    name: client_res_body_chunked_with_trailer_titlecase,
+
+    server:
+        expected: "GET / HTTP/1.1\r\nte: trailers\r\nhost: {addr}\r\n\r\n",
+        reply: "\
+            HTTP/1.1 200 OK\r\n\
+            transfer-encoding: chunked\r\n\
+            trailer: Chunky-Trailer\r\n\
+            \r\n\
+            5\r\n\
+            hello\r\n\
+            0\r\n\
+            chunky-trailer: header data\r\n\
+            \r\n\
+            ",
+
+    client:
+        request: {
+            method: GET,
+            url: "http://{addr}/",
+            headers: {
+                "te" => "trailers",
+            },
+        },
+        response:
+            status: OK,
+            headers: {
+                "Transfer-Encoding" => "chunked",
+            },
+            body: &b"hello"[..],
+            trailers: {
+                "chunky-trailer" => "header data",
+            },
+}
+
 test! {
     name: client_res_body_chunked_with_pathological_trailers,
 
diff --git a/tests/server.rs b/tests/server.rs
index 485a10e049..1cd0eba570 100644
--- a/tests/server.rs
+++ b/tests/server.rs
@@ -2850,6 +2850,51 @@ fn http1_trailer_send_fields() {
     assert_eq!(body, expected_body);
 }
 
+#[test]
+fn http1_trailer_send_fields_titlecase() {
+    let body = futures_util::stream::once(async move { Ok("hello".into()) });
+    let mut headers = HeaderMap::new();
+    headers.insert("chunky-trailer", "header data".parse().unwrap());
+    // Invalid trailer field that should not be sent
+    headers.insert("Host", "www.example.com".parse().unwrap());
+    // Not specified in Trailer header, so should not be sent
+    headers.insert("foo", "bar".parse().unwrap());
+
+    let server = serve();
+    server
+        .reply()
+        .header("transfer-encoding", "chunked")
+        .header("trailer", "Chunky-Trailer")
+        .body_stream_with_trailers(body, headers);
+    let mut req = connect(server.addr());
+    req.write_all(
+        b"\
+        GET / HTTP/1.1\r\n\
+        Host: example.domain\r\n\
+        Connection: keep-alive\r\n\
+        TE: trailers\r\n\
+        \r\n\
+    ",
+    )
+    .expect("writing");
+
+    let chunky_trailer_chunk = b"\r\nchunky-trailer: header data\r\n\r\n";
+    let res = read_until(&mut req, |buf| buf.ends_with(chunky_trailer_chunk)).expect("reading");
+    let sres = s(&res);
+
+    let expected_head =
+        "HTTP/1.1 200 OK\r\ntransfer-encoding: chunked\r\ntrailer: Chunky-Trailer\r\n";
+    assert_eq!(&sres[..expected_head.len()], expected_head);
+
+    // skip the date header
+    let date_fragment = "GMT\r\n\r\n";
+    let pos = sres.find(date_fragment).expect("find GMT");
+    let body = &sres[pos + date_fragment.len()..];
+
+    let expected_body = "5\r\nhello\r\n0\r\nchunky-trailer: header data\r\n\r\n";
+    assert_eq!(body, expected_body);
+}
+
 #[test]
 fn http1_trailer_fields_not_allowed() {
     let body = futures_util::stream::once(async move { Ok("hello".into()) });