diff --git a/website/Page Name Rules.md b/website/Page Name Rules.md
index 7c6ef5eb..57d4a886 100644
--- a/website/Page Name Rules.md	
+++ b/website/Page Name Rules.md	
@@ -3,4 +3,5 @@ There are a few rules regarding page names:
 * Page names cannot be empty
 * Page names cannot start with a `.`
 * Page names cannot `@` or `$`, due to ambiguity with referencing specific positions or anchors inside a page
+* Page names should not contain `!`
 * Page names cannot end with a _file extension_ containing just letters. That is, a page name like `test.md` is not allowed, whereas `test.123` would be.
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