diff --git a/tests/model_executor/models/qwen3_omni/test_qwen3_omni_quantization.py b/tests/model_executor/models/qwen3_omni/test_qwen3_omni_quantization.py
new file mode 100644
index 000000000..382e2f4d1
--- /dev/null
+++ b/tests/model_executor/models/qwen3_omni/test_qwen3_omni_quantization.py
@@ -0,0 +1,62 @@
+# SPDX-License-Identifier: Apache-2.0
+# SPDX-FileCopyrightText: Copyright contributors to the vLLM-Omni project
+"""Regression tests for nested Qwen3-Omni quantization config mapping."""
+
+from dataclasses import dataclass
+
+import pytest
+
+from vllm_omni.model_executor.models.qwen3_omni.quantization import (
+    _OUTER_MAPPING_APPLIED,
+    apply_nested_quant_config_mapping,
+)
+
+pytestmark = [pytest.mark.core_model, pytest.mark.cpu]
+
+
+@dataclass
+class _QuantConfig:
+    packed_modules_mapping: dict[str, list[str]]
+
+
+@dataclass
+class _NestedModel:
+    quant_config: _QuantConfig | None
+
+
+@dataclass
+class _NestedModelWithPackedModules(_NestedModel):
+    packed_modules_mapping: dict[str, list[str]]
+
+
+def _mapped_quant_config(**packed_modules_mapping):
+    quant_config = _QuantConfig(packed_modules_mapping=packed_modules_mapping)
+    setattr(quant_config, _OUTER_MAPPING_APPLIED, True)
+    return quant_config
+
+
+def test_nested_mapping_ignores_missing_quant_config():
+    apply_nested_quant_config_mapping(_NestedModel(quant_config=None))
+
+
+def test_nested_mapping_allows_model_without_packed_modules_mapping():
+    quant_config = _mapped_quant_config(existing=["module"])
+
+    apply_nested_quant_config_mapping(_NestedModel(quant_config=quant_config))
+
+    assert quant_config.packed_modules_mapping == {"existing": ["module"]}
+
+
+def test_nested_mapping_merges_packed_modules_mapping():
+    quant_config = _mapped_quant_config(existing=["module"])
+    model = _NestedModelWithPackedModules(
+        quant_config=quant_config,
+        packed_modules_mapping={"qkv_proj": ["q_proj", "k_proj", "v_proj"]},
+    )
+
+    apply_nested_quant_config_mapping(model)
+
+    assert quant_config.packed_modules_mapping == {
+        "existing": ["module"],
+        "qkv_proj": ["q_proj", "k_proj", "v_proj"],
+    }
diff --git a/vllm_omni/model_executor/models/qwen3_omni/quantization.py b/vllm_omni/model_executor/models/qwen3_omni/quantization.py
index d870c7abd..26fe46956 100644
--- a/vllm_omni/model_executor/models/qwen3_omni/quantization.py
+++ b/vllm_omni/model_executor/models/qwen3_omni/quantization.py
@@ -1,5 +1,5 @@
 # SPDX-License-Identifier: Apache-2.0
-# SPDX-FileCopyrightText: Copyright contributors to the vLLM project
+# SPDX-FileCopyrightText: Copyright contributors to the vLLM-Omni project
 """Quantization mapping helpers for nested Qwen3-Omni stages."""
 
 from vllm.model_executor.models.interfaces import SupportsQuant
@@ -25,8 +25,8 @@ def apply_nested_quant_config_mapping(model: SupportsQuant) -> None:
 
     # The outer model maps names, while the nested model still contributes
     # fused-module metadata needed by quantization scheme matching.
-    if model.packed_modules_mapping is not None:
-        quant_config.packed_modules_mapping.update(model.packed_modules_mapping)
+    if packed_modules_mapping := getattr(model, "packed_modules_mapping", None):
+        quant_config.packed_modules_mapping.update(packed_modules_mapping)
 
 
 class Qwen3OmniNestedSupportsQuant(SupportsQuant):