diff --git a/docs/negation-types.md b/docs/negation-types.md
index bc0eecf..9a6dd59 100644
--- a/docs/negation-types.md
+++ b/docs/negation-types.md
@@ -20,7 +20,7 @@ We propose to allow users to write such a type. Formally:
 
 ```ebnf
 ty ::= `~` ty
-     | name [`<` [ty] {`,` ty} `>`]
+     | name [`<` [ty {`,` ty}] `>`]
      | ty {`|` ty}
      | ty {`&` ty}
      | `(` ty `)`