diff --git a/umskt/src/key.rs b/umskt/src/key.rs
index 4dea89b..562a8a2 100644
--- a/umskt/src/key.rs
+++ b/umskt/src/key.rs
@@ -6,7 +6,7 @@ use openssl::bn::BigNum;
 const PK_LENGTH: usize = 25;
 
 /// The allowed character set in a product key.
-pub const KEY_CHARSET: [char; 24] = [
+pub(crate) const KEY_CHARSET: [char; 24] = [
     'B', 'C', 'D', 'F', 'G', 'H', 'J', 'K', 'M', 'P', 'Q', 'R', 'T', 'V', 'W', 'X', 'Y', '2', '3',
     '4', '6', '7', '8', '9',
 ];