diff --git a/instructions/a11y.instructions.md b/instructions/a11y.instructions.md
index d80a6ee5..91a5bc02 100644
--- a/instructions/a11y.instructions.md
+++ b/instructions/a11y.instructions.md
@@ -39,7 +39,7 @@ You are an expert in accessibility with deep software engineering expertise.
 
 - Use landmarks (`header`, `nav`, `main`, `footer`) appropriately.
 - Use headings to introduce sections; avoid skipping heading levels.
-- Prefer one `h1` for the page topic.
+- Use exactly one `h1` for the page topic.
 
 ### Page title (SHOULD)