diff --git a/src/anthropic/lib/middleware/_fallbacks.py b/src/anthropic/lib/middleware/_fallbacks.py
index 15edbc232..cb6426392 100644
--- a/src/anthropic/lib/middleware/_fallbacks.py
+++ b/src/anthropic/lib/middleware/_fallbacks.py
@@ -431,7 +431,9 @@ def _splice_fallback_stream(
             pin=pin,
         )
         return APIResponse(
-            raw=_spliced_http_response(response.http_response, _FrameByteStream(frames)),
+            raw=_spliced_http_response(
+                response.http_response, _FrameByteStream(frames, response=response.http_response)
+            ),
             cast_to=response._cast_to,
             client=response._client,
             stream=True,
@@ -461,7 +463,9 @@ def _splice_fallback_stream_async(
             pin=pin,
         )
         return AsyncAPIResponse(
-            raw=_spliced_http_response(response.http_response, _AsyncFrameByteStream(frames)),
+            raw=_spliced_http_response(
+                response.http_response, _AsyncFrameByteStream(frames, response=response.http_response)
+            ),
             cast_to=response._cast_to,
             client=response._client,
             stream=True,
@@ -1692,8 +1696,9 @@ def _spliced_http_response(
 
 
 class _FrameByteStream(httpx2.SyncByteStream):
-    def __init__(self, frames: Generator[bytes, None, None]) -> None:
+    def __init__(self, frames: Generator[bytes, None, None], *, response: httpx2.Response) -> None:
         self._frames = frames
+        self._response = response
 
     @override
     def __iter__(self) -> Iterator[bytes]:
@@ -1701,12 +1706,17 @@ def __iter__(self) -> Iterator[bytes]:
 
     @override
     def close(self) -> None:
-        self._frames.close()
+        try:
+            self._frames.close()
+        finally:
+            # An unread generator never enters its finally block.
+            self._response.close()
 
 
 class _AsyncFrameByteStream(httpx2.AsyncByteStream):
-    def __init__(self, frames: AsyncGenerator[bytes, None]) -> None:
+    def __init__(self, frames: AsyncGenerator[bytes, None], *, response: httpx2.Response) -> None:
         self._frames = frames
+        self._response = response
 
     @override
     def __aiter__(self) -> AsyncIterator[bytes]:
@@ -1714,4 +1724,8 @@ def __aiter__(self) -> AsyncIterator[bytes]:
 
     @override
     async def aclose(self) -> None:
-        await self._frames.aclose()
+        try:
+            await self._frames.aclose()
+        finally:
+            # An unread generator never enters its finally block.
+            await self._response.aclose()
diff --git a/tests/lib/test_refusal_fallback_streaming.py b/tests/lib/test_refusal_fallback_streaming.py
index e130240df..8de9261d9 100644
--- a/tests/lib/test_refusal_fallback_streaming.py
+++ b/tests/lib/test_refusal_fallback_streaming.py
@@ -6,6 +6,7 @@
 import logging
 from typing import Any, List, Protocol, cast
 from pathlib import Path
+from unittest.mock import Mock
 from typing_extensions import Literal
 
 import httpx2
@@ -1303,6 +1304,36 @@ def test_entry_overrides_apply_to_the_hop_request(self, respx_mock: MockRouter)
 
 
 class TestCancellation:
+    def test_closing_an_unread_stream_closes_the_underlying_response(self) -> None:
+        response = httpx2.Response(
+            200, headers={"content-type": "text/event-stream"}, stream=httpx2.ByteStream(STREAM_A.encode())
+        )
+        handler = Mock(return_value=response)
+        with make_sync_client(
+            http_client=httpx2.Client(transport=httpx2.MockTransport(handler)),
+            middleware=[BetaRefusalFallbackMiddleware(FALLBACKS)],
+        ) as client:
+            with create_stream(client):
+                assert not response.is_closed
+
+            assert response.is_closed
+        handler.assert_called_once()
+
+    async def test_closing_an_unread_async_stream_closes_the_underlying_response(self) -> None:
+        response = httpx2.Response(
+            200, headers={"content-type": "text/event-stream"}, stream=httpx2.ByteStream(STREAM_A.encode())
+        )
+        handler = Mock(return_value=response)
+        async with make_async_client(
+            http_client=httpx2.AsyncClient(transport=httpx2.MockTransport(handler)),
+            middleware=[BetaRefusalFallbackMiddleware(FALLBACKS)],
+        ) as client:
+            async with await create_stream_async(client):
+                assert not response.is_closed
+
+            assert response.is_closed
+        handler.assert_called_once()
+
     @pytest.mark.respx(base_url=base_url)
     def test_closing_the_stream_mid_passthrough_tears_down_without_a_fallback_request(
         self, respx_mock: MockRouter