diff --git a/src/anthropic/lib/bedrock/_stream_decoder.py b/src/anthropic/lib/bedrock/_stream_decoder.py
index f77c2a329..bcbf498d2 100644
--- a/src/anthropic/lib/bedrock/_stream_decoder.py
+++ b/src/anthropic/lib/bedrock/_stream_decoder.py
@@ -68,7 +68,9 @@ def _parse_message_from_event(self, event: EventStreamMessage) -> ServerSentEven
         return _chunk_bytes_to_sse(chunk.get("bytes"))
 
 
-def _chunk_bytes_to_sse(raw: bytes) -> ServerSentEvent | None:
+def _chunk_bytes_to_sse(raw: bytes | None) -> ServerSentEvent | None:
+    if not isinstance(raw, bytes):
+        return None
     decoded = raw.decode()
     data: Any
     try:
diff --git a/tests/lib/test_bedrock.py b/tests/lib/test_bedrock.py
index bc97af03f..d923371bf 100644
--- a/tests/lib/test_bedrock.py
+++ b/tests/lib/test_bedrock.py
@@ -348,6 +348,10 @@ def test_chunk_bytes_to_sse_drops_chunk_without_type_or_completion() -> None:
     assert _chunk_bytes_to_sse(raw) is None
 
 
+def test_chunk_bytes_to_sse_handles_none_or_non_bytes() -> None:
+    assert _chunk_bytes_to_sse(None) is None
+
+
 def _eventstream_chunk_frame(payload: t.Mapping[str, object]) -> bytes:
     """Encode `payload` as one `chunk` event in AWS eventstream binary framing."""
     body = json.dumps({"bytes": base64.b64encode(json.dumps(payload).encode()).decode()}).encode()