diff --git a/src/mode/serialization.rs b/src/mode/serialization.rs
index 915d8c5..ff59435 100644
--- a/src/mode/serialization.rs
+++ b/src/mode/serialization.rs
@@ -44,12 +44,8 @@ pub trait Deserializer {
 }
 
 /// Extension trait for [Deserializer]s.
-pub trait DeserializerExt {
+pub trait DeserializerExt: Deserializer {
     /// Try to read exactly `N` bytes.
-    fn read_n_const<const N: usize>(&mut self) -> Result<[u8; N], &[u8]>;
-}
-
-impl<D: ?Sized + Deserializer> DeserializerExt for D {
     fn read_n_const<const N: usize>(&mut self) -> Result<[u8; N], &[u8]> {
         let slice = self.read_n(N);
         match slice.try_into() {
@@ -58,3 +54,5 @@ impl<D: ?Sized + Deserializer> DeserializerExt for D {
         }
     }
 }
+
+impl<D: ?Sized + Deserializer> DeserializerExt for D {}