diff --git a/spec/syntax.md b/spec/syntax.md
index 85db09d40f..9e1411f9d8 100644
--- a/spec/syntax.md
+++ b/spec/syntax.md
@@ -461,6 +461,16 @@ A _key_ can be either a _literal_ value or the "catch-all" key `*`.
 The **_<dfn>catch-all key</dfn>_** is a special key, represented by `*`,
 that matches all values for a given _selector_.
 
+> [!NOTE]
+> To represent a _key_ consisting of the character `*` U+002A ASTERISK,
+> use a _quoted literal_:
+> ```
+> .input {$value :string}
+> .match $value
+> |*| {{Matches the string *}}
+> *   {{Matches any other string}}
+> ```
+
 The value of each _literal_ _key_ MUST be treated as if it were in
 [Unicode Normalization Form C](https://unicode.org/reports/tr15/) ("NFC").
 Two _literal_ _keys_ are considered equal if they are canonically equivalent strings,