diff --git a/packages/connect-node/src/handler.ts b/packages/connect-node/src/handler.ts
index d334b88ae..bcbf90b3f 100644
--- a/packages/connect-node/src/handler.ts
+++ b/packages/connect-node/src/handler.ts
@@ -99,7 +99,12 @@ export function createHandler<M extends MethodInfo>(
     res: http.ServerResponse | http2.Http2ServerResponse
   ): void {
     if (method.kind == MethodKind.BiDiStreaming && req.httpVersionMajor !== 2) {
-      return void endWithHttpStatus(res, 505, "Version Not Supported");
+      // Clients coded to expect full-duplex connections may hang if they've
+      // mistakenly negotiated HTTP/1.1. To unblock them, we must close the
+      // underlying TCP connection.
+      return void endWithHttpStatus(res, 505, "Version Not Supported", {
+        Connection: "close",
+      });
     }
     if (req.method !== "POST") {
       // The gRPC-HTTP2, gRPC-Web, and Connect protocols are all POST-only.
diff --git a/packages/connect-node/src/private/io.ts b/packages/connect-node/src/private/io.ts
index 00d8c166e..83da8e88a 100644
--- a/packages/connect-node/src/private/io.ts
+++ b/packages/connect-node/src/private/io.ts
@@ -19,7 +19,10 @@ import { assert } from "./assert.js";
 import type { ReadableStreamReadResultLike } from "../lib.dom.streams.js";
 import { Code, ConnectError, EnvelopedMessage } from "@bufbuild/connect-core";
 import type { JsonValue } from "@bufbuild/protobuf";
-import { nodeHeaderToWebHeader } from "./web-header-to-node-headers.js";
+import {
+  nodeHeaderToWebHeader,
+  webHeaderToNodeHeaders,
+} from "./web-header-to-node-headers.js";
 
 export function jsonParse(bytes: Uint8Array): JsonValue {
   const buf = bytes instanceof Buffer ? bytes : Buffer.from(bytes);
@@ -197,13 +200,17 @@ export function readToEnd(stream: stream.Readable): Promise<Uint8Array> {
 export async function endWithHttpStatus(
   res: http.ServerResponse | http2.Http2ServerResponse,
   statusCode: number,
-  statusMessage: string
+  statusMessage: string,
+  header?: HeadersInit
 ): Promise<void> {
+  const headers: http.OutgoingHttpHeaders | undefined = header
+    ? webHeaderToNodeHeaders(header)
+    : undefined;
   if ("createPushResponse" in res) {
     // this is a HTTP/2 response, which does not support status messages
-    res.writeHead(statusCode);
+    res.writeHead(statusCode, headers);
   } else {
-    res.writeHead(statusCode, statusMessage);
+    res.writeHead(statusCode, statusMessage, headers);
   }
   await end(res);
 }