diff --git a/python/sglang/srt/entrypoints/openai/serving_chat.py b/python/sglang/srt/entrypoints/openai/serving_chat.py
index 973ae28ce..5b31de242 100644
--- a/python/sglang/srt/entrypoints/openai/serving_chat.py
+++ b/python/sglang/srt/entrypoints/openai/serving_chat.py
@@ -785,8 +785,9 @@ class OpenAIServingChat(OpenAIServingBase):
                     prompt_ids = self.tokenizer_manager.tokenizer.encode(
                         rendered_prompt, **encode_kwargs
                     )
-                except jinja2.TemplateError as template_error:
+                except (jinja2.TemplateError, TypeError) as template_error:
                     # Template errors (e.g., from raise_exception in Jinja templates)
+                    # and TypeError (e.g., tojson filter on Jinja2 Undefined variables)
                     # should be treated as client errors (400 BadRequest)
                     raise ValueError(str(template_error)) from template_error