diff --git a/src/diffusers/pipelines/longcat_audio_dit/pipeline_longcat_audio_dit.py b/src/diffusers/pipelines/longcat_audio_dit/pipeline_longcat_audio_dit.py
index e6478535b373..d5cd70c9f6d5 100644
--- a/src/diffusers/pipelines/longcat_audio_dit/pipeline_longcat_audio_dit.py
+++ b/src/diffusers/pipelines/longcat_audio_dit/pipeline_longcat_audio_dit.py
@@ -291,7 +291,10 @@ def __call__(
                 negative_prompt = [negative_prompt] * batch_size
             else:
                 negative_prompt = list(negative_prompt)
-            negative_prompt_embeds, negative_prompt_embeds_len = self.encode_prompt(negative_prompt, device)
+            normalized_negative_prompts = [_normalize_text(text) for text in negative_prompt]
+            negative_prompt_embeds, negative_prompt_embeds_len = self.encode_prompt(
+                normalized_negative_prompts, device
+            )
             negative_prompt_embeds_mask = _lens_to_mask(
                 negative_prompt_embeds_len, length=negative_prompt_embeds.shape[1]
             )