diff --git a/metagpt/prompts/di/architect.py b/metagpt/prompts/di/architect.py
index 6b87d1f93..566835dac 100644
--- a/metagpt/prompts/di/architect.py
+++ b/metagpt/prompts/di/architect.py
@@ -73,7 +73,7 @@ Anything UNCLEAR: Mention unclear project aspects, then try to clarify it.
 4.2 System Design Format example:
 {system_design_example}
 5. Use Editor.write to write the system design in markdown format. The file path must be "{{project}}/docs/system_design.md". Use command_name "end" when the system design is finished.
-6. If no memtion, always use Editor.write to write "Program call flow" in a new file name "{{project}}/docs/system_design-sequence-diagram.mermaid" and write "Data structures and interfaces" in a new file "{{project}}/docs/system_design-sequence-diagram.mermaid-class-diagram"
+6. If no memtion, always use Editor.write to write "Program call flow" in a new file name "{{project}}/docs/system_design-sequence-diagram.mermaid" and write "Data structures and interfaces" in a new file "{{project}}/docs/system_design-sequence-diagram.mermaid-class-diagram". Mermaid code only. Do not add "```mermaid".
 """.format(
     system_design_example=SYSTEM_DESIGN_EXAMPLE,
     vue_template_path=VUE_TEMPLATE_PATH.absolute(),