diff --git a/litellm/proxy/litellm_pre_call_utils.py b/litellm/proxy/litellm_pre_call_utils.py
index fc81f07c7f2..a1ed2287e7c 100644
--- a/litellm/proxy/litellm_pre_call_utils.py
+++ b/litellm/proxy/litellm_pre_call_utils.py
@@ -121,7 +121,7 @@ def _trace_id_from_otel_span(span: "OtelSpan | None") -> str | None:
 def add_otel_trace_id_to_request(
     data: dict[str, object], _metadata_variable_name: str, parent_otel_span: "OtelSpan | None"
 ) -> None:
-    if "litellm_trace_id" in data:
+    if data.get("litellm_trace_id"):
         return
     metadata: Final = data.get(_metadata_variable_name)
     if isinstance(metadata, dict) and metadata.get("trace_id"):
@@ -131,7 +131,7 @@ def add_otel_trace_id_to_request(
         return
     data["litellm_trace_id"] = trace_id  # rebind-ok: data is an out-param
     if isinstance(metadata, dict):
-        metadata["trace_id"] = trace_id
+        metadata["trace_id"] = trace_id  # rebind-ok: metadata is the request's own out-param dict
 
 
 def _session_id_from_baggage(baggage: str) -> str | None:
diff --git a/tests/test_litellm/proxy/test_litellm_pre_call_utils.py b/tests/test_litellm/proxy/test_litellm_pre_call_utils.py
index 81ec555b59c..1573845b8e3 100644
--- a/tests/test_litellm/proxy/test_litellm_pre_call_utils.py
+++ b/tests/test_litellm/proxy/test_litellm_pre_call_utils.py
@@ -3605,6 +3605,23 @@ async def test_add_litellm_data_to_request_otel_span_does_not_override_caller_tr
     assert from_body["metadata"]["trace_id"] == "body-trace"
 
 
+@pytest.mark.asyncio
+@pytest.mark.parametrize("empty_trace_id", [None, ""])
+async def test_add_litellm_data_to_request_otel_span_fills_empty_body_trace_id(empty_trace_id):
+    """A serialized-but-empty litellm_trace_id in the body (null or "") carries
+    no identity, so it must not block the OTel server span fallback."""
+    otel_trace_id = 0x4BF92F3577B34DA6A3CE929D0E0E4736
+    data = await add_litellm_data_to_request(
+        data={"model": "gpt-5.6", "litellm_trace_id": empty_trace_id},
+        request=_request_mock_without_trace_headers(),
+        user_api_key_dict=UserAPIKeyAuth(api_key="hashed-key", parent_otel_span=_otel_span_with_trace_id(otel_trace_id)),
+        proxy_config=MagicMock(),
+        general_settings={},
+    )
+    assert data["litellm_trace_id"] == format(otel_trace_id, "032x")
+    assert data["metadata"]["trace_id"] == format(otel_trace_id, "032x")
+
+
 @pytest.mark.asyncio
 @pytest.mark.parametrize("parent_otel_span", [None, "invalid_span", "not_a_span"])
 async def test_add_litellm_data_to_request_no_trace_id_without_valid_otel_span(parent_otel_span):