diff --git a/src/error.rs b/src/error.rs
index 1180295..8a4a206 100644
--- a/src/error.rs
+++ b/src/error.rs
@@ -1,4 +1,5 @@
 use crate::ikm::IkmId;
+use crate::scheme::SchemeSerializeType;
 
 pub(crate) type Result<T, E = Error> = core::result::Result<T, E>;
 
@@ -19,7 +20,7 @@ pub enum Error {
 	#[error("parsing error: ikm: invalid data length: {0} bytes")]
 	ParsingIkmInvalidLength(usize),
 	#[error("parsing error: scheme: {0}: unknown scheme")]
-	ParsingSchemeUnknownScheme(u32),
+	ParsingSchemeUnknownScheme(SchemeSerializeType),
 	#[error("unable to generate random values: {0}")]
 	RandomSourceError(getrandom::Error),
 	#[error("system time error: {0}")]
diff --git a/src/ikm.rs b/src/ikm.rs
index 24a63bb..87ee50e 100644
--- a/src/ikm.rs
+++ b/src/ikm.rs
@@ -1,5 +1,5 @@
 use crate::error::{Error, Result};
-use crate::Scheme;
+use crate::scheme::{Scheme, SchemeSerializeType};
 use base64ct::{Base64UrlUnpadded, Encoding};
 use std::time::{Duration, SystemTime};
 
@@ -24,7 +24,7 @@ impl InputKeyMaterial {
 	fn as_bytes(&self) -> Result<[u8; IKM_STRUCT_SIZE]> {
 		let mut res = Vec::with_capacity(IKM_STRUCT_SIZE);
 		res.extend_from_slice(&self.id.to_le_bytes());
-		res.extend_from_slice(&(self.scheme as u32).to_le_bytes());
+		res.extend_from_slice(&(self.scheme as SchemeSerializeType).to_le_bytes());
 		res.extend_from_slice(&self.content);
 		res.extend_from_slice(
 			&self
@@ -47,7 +47,7 @@ impl InputKeyMaterial {
 	pub(crate) fn from_bytes(b: [u8; IKM_STRUCT_SIZE]) -> Result<Self> {
 		Ok(Self {
 			id: IkmId::from_le_bytes(b[0..4].try_into().unwrap()),
-			scheme: u32::from_le_bytes(b[4..8].try_into().unwrap()).try_into()?,
+			scheme: SchemeSerializeType::from_le_bytes(b[4..8].try_into().unwrap()).try_into()?,
 			content: b[8..40].try_into().unwrap(),
 			created_at: InputKeyMaterial::bytes_to_system_time(&b[40..48])?,
 			expire_at: InputKeyMaterial::bytes_to_system_time(&b[48..56])?,
diff --git a/src/scheme.rs b/src/scheme.rs
index 4afea4e..da67e0c 100644
--- a/src/scheme.rs
+++ b/src/scheme.rs
@@ -2,6 +2,8 @@ use crate::encryption::EncryptionFunction;
 use crate::kdf::KdfFunction;
 use crate::Error;
 
+pub(crate) type SchemeSerializeType = u32;
+
 #[derive(Copy, Clone, Debug, PartialEq)]
 pub enum Scheme {
 	XChaCha20Poly1305WithBlake3 = 1,
@@ -23,10 +25,10 @@ impl Scheme {
 	}
 }
 
-impl TryFrom<u32> for Scheme {
+impl TryFrom<SchemeSerializeType> for Scheme {
 	type Error = Error;
 
-	fn try_from(value: u32) -> Result<Self, Self::Error> {
+	fn try_from(value: SchemeSerializeType) -> Result<Self, Self::Error> {
 		match value {
 			1 => Ok(Scheme::XChaCha20Poly1305WithBlake3),
 			_ => Err(Error::ParsingSchemeUnknownScheme(value)),