diff --git a/packages/connect-web-bench/README.md b/packages/connect-web-bench/README.md
index 6fc01fc42..0cdf05480 100644
--- a/packages/connect-web-bench/README.md
+++ b/packages/connect-web-bench/README.md
@@ -10,5 +10,5 @@ it like a web server would usually do.
 
 | code generator | bundle size        | minified               | compressed           |
 |----------------|-------------------:|-----------------------:|---------------------:|
-| connect        | 112,186 b | 49,484 b | 13,326 b |
+| connect        | 112,396 b | 49,571 b | 13,350 b |
 | grpc-web       | 414,071 b    | 300,352 b    | 53,255 b |
diff --git a/packages/connect/src/protocol/run-call.spec.ts b/packages/connect/src/protocol/run-call.spec.ts
index 6bb7233b9..0fcc38e74 100644
--- a/packages/connect/src/protocol/run-call.spec.ts
+++ b/packages/connect/src/protocol/run-call.spec.ts
@@ -232,4 +232,31 @@ describe("runStreamingCall()", function () {
     const it = req.message[Symbol.asyncIterator]();
     expect(await it.next()).toEqual({ done: true, value: undefined });
   });
+  it("should propagate the error thrown in next", async function () {
+    const req = makeReq();
+    let reqError: Error | undefined;
+    req.message = {
+      [Symbol.asyncIterator]() {
+        return {
+          next() {
+            fail("unexpected call");
+            throw new Error("unexpected call");
+          },
+          throw(e) {
+            reqError = e as Error;
+            return Promise.reject({ done: true, value: undefined });
+          },
+        };
+      },
+    };
+    await expectAsync(
+      runStreamingCall<Int32Value, StringValue>({
+        req: req,
+        next() {
+          return Promise.reject(new Error("foo"));
+        },
+      }),
+    ).toBeRejectedWithError("[unknown] foo");
+    expect(reqError?.message).toEqual("[unknown] foo");
+  });
 });
diff --git a/packages/connect/src/protocol/run-call.ts b/packages/connect/src/protocol/run-call.ts
index 0edae2a15..e3a988356 100644
--- a/packages/connect/src/protocol/run-call.ts
+++ b/packages/connect/src/protocol/run-call.ts
@@ -105,18 +105,28 @@ export function runStreamingCall<
     message: normalizeIterable(opt.req.method.I, opt.req.message),
     signal,
   };
+  let doneCalled = false;
   // Call return on the request iterable to indicate
   // that we will no longer consume it and it should
   // cleanup any allocated resources.
   signal.addEventListener("abort", function () {
-    opt.req.message[Symbol.asyncIterator]()
-      .return?.()
-      .catch(() => {
-        // return returns a promise, which we don't care about.
+    const it = opt.req.message[Symbol.asyncIterator]();
+    // If the signal is aborted due to an error, we want to throw
+    // the error to the request iterator.
+    if (!doneCalled) {
+      it.throw?.(this.reason).catch(() => {
+        // throw returns a promise, which we don't care about.
         //
         // Uncaught promises are thrown at sometime/somewhere by the event loop,
         // this is to ensure error is caught and ignored.
       });
+    }
+    it.return?.().catch(() => {
+      // return returns a promise, which we don't care about.
+      //
+      // Uncaught promises are thrown at sometime/somewhere by the event loop,
+      // this is to ensure error is caught and ignored.
+    });
   });
   return next(req).then((res) => {
     return {
@@ -128,6 +138,7 @@ export function runStreamingCall<
             next() {
               return it.next().then((r) => {
                 if (r.done == true) {
+                  doneCalled = true;
                   done();
                 }
                 return r;