diff --git a/vllm_omni/engine/arg_utils.py b/vllm_omni/engine/arg_utils.py
index 202281e068..0a38f65de7 100644
--- a/vllm_omni/engine/arg_utils.py
+++ b/vllm_omni/engine/arg_utils.py
@@ -52,7 +52,10 @@ def create_model_config(self) -> OmniModelConfig:
         # and adding the new omni-specific fields
         config_dict = base_config.__dict__.copy()
         # FIXME(Isotr0py): This is a temporary workaround for multimodal_config
-        config_dict = {**config_dict.pop("multimodal_config", {}).__dict__, **config_dict}
+        config_dict = {
+            **(getattr(mm := config_dict.pop("multimodal_config", None), "__dict__", mm or {})),
+            **config_dict,
+        }
 
         # Add the new omni-specific fields
         config_dict["stage_id"] = self.stage_id