diff --git a/lrpar/src/lib/ctbuilder.rs b/lrpar/src/lib/ctbuilder.rs
index 98197b5c2..234815b20 100644
--- a/lrpar/src/lib/ctbuilder.rs
+++ b/lrpar/src/lib/ctbuilder.rs
@@ -170,6 +170,7 @@ pub enum Visibility {
 ///
 /// [Rust Edition]: https://doc.rust-lang.org/edition-guide/rust-2021/index.html
 #[derive(Clone, Copy, PartialEq, Eq, Debug)]
+#[non_exhaustive]
 pub enum RustEdition {
     Rust2015,
     Rust2018,