diff --git a/src/client/body/stream.rs b/src/client/body/stream.rs
index d7b8d9e6..68ac7504 100644
--- a/src/client/body/stream.rs
+++ b/src/client/body/stream.rs
@@ -7,7 +7,7 @@ use std::{
 use bytes::Bytes;
 use futures_util::{FutureExt, Stream, StreamExt, stream::BoxStream};
 use http_body_util::BodyExt;
-use pyo3::{coroutine::CancelHandle, intern, prelude::*};
+use pyo3::{coroutine::CancelHandle, exceptions::PyStopIteration, intern, prelude::*};
 use tokio::{sync::Mutex, task::JoinHandle};
 
 use crate::{
@@ -225,10 +225,10 @@ impl Stream for PyStream {
                     PyStreamSource::Sync(ref ob) => {
                         let ob = ob.clone();
                         runtime.spawn_blocking(move || {
-                            error::attach(|py| {
-                                ob.call_method0(py, intern!(py, "__next__"))
-                                    .ok()
-                                    .map(|ob| ob.extract(py))
+                            error::attach(|py| match ob.call_method0(py, intern!(py, "__next__")) {
+                                Ok(ob) => Some(ob.extract(py)),
+                                Err(err) if err.is_instance_of::<PyStopIteration>(py) => None,
+                                Err(err) => Some(Err(err)),
                             })
                             .unwrap_or_else(|err| Some(Err(err.into())))
                         })
diff --git a/tests/sync_upload_test.py b/tests/sync_upload_test.py
new file mode 100644
index 00000000..a419809d
--- /dev/null
+++ b/tests/sync_upload_test.py
@@ -0,0 +1,119 @@
+import asyncio
+import threading
+from contextlib import asynccontextmanager
+
+import pytest
+import wreq
+
+
+@asynccontextmanager
+async def upload_server():
+    bodies = asyncio.Queue()
+    handlers = set()
+    writers = []
+    errors = []
+
+    async def accept(reader, writer):
+        task = asyncio.current_task()
+        handlers.add(task)
+        writers.append(writer)
+        try:
+            header = await asyncio.wait_for(reader.readuntil(b"\r\n\r\n"), 5)
+            assert b"transfer-encoding: chunked" in header.lower()
+            body = bytearray()
+            while True:
+                line = await asyncio.wait_for(reader.readline(), 5)
+                if not line:
+                    return
+                size = int(line, 16)
+                if not size:
+                    assert await reader.readexactly(2) == b"\r\n"
+                    break
+                body.extend(await asyncio.wait_for(reader.readexactly(size), 5))
+                assert await reader.readexactly(2) == b"\r\n"
+            bodies.put_nowait(bytes(body))
+            writer.write(
+                b"HTTP/1.1 200 OK\r\nConnection: close\r\nContent-Length: 2\r\n\r\nok"
+            )
+            await writer.drain()
+        except (asyncio.IncompleteReadError, ConnectionError):
+            # A rejected upload can close before any headers or terminal chunk.
+            pass
+        except Exception as error:
+            errors.append(error)
+        finally:
+            writer.close()
+            handlers.discard(task)
+
+    server = await asyncio.start_server(accept, "127.0.0.1", 0)
+    try:
+        yield f"http://127.0.0.1:{server.sockets[0].getsockname()[1]}/", bodies
+    finally:
+        server.close()
+        for writer in writers:
+            writer.close()
+        await asyncio.gather(
+            *(writer.wait_closed() for writer in writers), return_exceptions=True
+        )
+        await asyncio.gather(*handlers, return_exceptions=True)
+        await server.wait_closed()
+        assert not errors, errors
+
+
+@pytest.mark.asyncio
+@pytest.mark.parametrize("blocking", [False, True])
+@pytest.mark.parametrize("multipart", [False, True])
+async def test_sync_upload_iterator_errors(blocking, multipart):
+    factory = wreq.blocking.Client if blocking else wreq.Client
+    client = factory(proxies=[])
+    try:
+        async with upload_server() as (url, bodies):
+            for failure in (False, True):
+                finalized = threading.Event()
+
+                def chunks():
+                    try:
+                        yield b"hello"
+                        if failure:
+                            raise ValueError("upload exploded")
+                        yield " world"
+                    finally:
+                        finalized.set()
+
+                kwargs = (
+                    {
+                        "multipart": wreq.Multipart(
+                            wreq.Part(name="file", value=chunks())
+                        )
+                    }
+                    if multipart
+                    else {"body": chunks()}
+                )
+
+                def send_blocking():
+                    with client.post(url, **kwargs) as response:
+                        return response.bytes()
+
+                async def send():
+                    if blocking:
+                        return await asyncio.to_thread(send_blocking)
+                    response = await client.post(url, **kwargs)
+                    async with response:
+                        return await response.bytes()
+
+                if failure:
+                    with pytest.raises(wreq.exceptions.RequestError) as caught:
+                        await asyncio.wait_for(send(), 5)
+                    assert "ValueError" in str(caught.value)
+                    assert "upload exploded" in str(caught.value)
+                else:
+                    assert await asyncio.wait_for(send(), 5) == b"ok"
+                    body = await asyncio.wait_for(bodies.get(), 5)
+                    assert (
+                        (b"hello world" in body)
+                        if multipart
+                        else (body == b"hello world")
+                    )
+                assert finalized.is_set()
+    finally:
+        client.close()