diff --git a/vllm/entrypoints/chat_utils.py b/vllm/entrypoints/chat_utils.py
index e3b727597d..e4e44bc01a 100644
--- a/vllm/entrypoints/chat_utils.py
+++ b/vllm/entrypoints/chat_utils.py
@@ -1517,7 +1517,7 @@ def _parse_chat_message_content_mm_part(
                 audio_url = audio_url.get("url", None)
             return "audio_url", audio_url
         if part.get("input_audio") is not None:
-            input_audio_params = cast(dict[str, str], part)
+            input_audio_params = _InputAudioParser(part).get("input_audio", None)
             return "input_audio", input_audio_params
         if "video_url" in part:
             video_params = cast(CustomChatCompletionContentSimpleVideoParam, part)