diff --git a/src/parse/matches/value_source.rs b/src/parse/matches/value_source.rs
index 05d7779b6a73..fb762d2af683 100644
--- a/src/parse/matches/value_source.rs
+++ b/src/parse/matches/value_source.rs
@@ -1,5 +1,6 @@
 /// Origin of the argument's value
 #[derive(Debug, Clone, Copy, PartialEq, Eq, PartialOrd, Ord)]
+#[non_exhaustive]
 pub enum ValueSource {
     /// Value came [`Arg::default_value`][crate::Arg::default_value]
     DefaultValue,