diff --git a/src/client.rs b/src/client.rs
index 8f9dc61..5cabcc9 100644
--- a/src/client.rs
+++ b/src/client.rs
@@ -5,7 +5,7 @@ use hyper::{self, header, mime};
 use rustc_serialize::json;
 use url::{Url, form_urlencoded};
 
-use super::{TokenPair, AccessToken, RefreshToken};
+use super::{TokenPair, AccessTokenType, AccessToken, RefreshToken};
 use super::error::{Error, Result, OAuth2Error, OAuth2ErrorCode};
 
 /// OAuth 2.0 client.
@@ -38,7 +38,10 @@ impl Into<TokenPair> for TokenResponse {
         TokenPair {
             access: AccessToken {
                 token: self.access_token,
-                token_type: self.token_type,
+                token_type: match &self.token_type[..] {
+                    "Bearer" | "bearer" => AccessTokenType::Bearer,
+                    _ => AccessTokenType::Unrecognized(self.token_type),
+                },
                 expires: self.expires_in.map(|s| UTC::now() + Duration::seconds(s)),
                 scope: self.scope,
             },
diff --git a/src/lib.rs b/src/lib.rs
index da4eecd..5098fab 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -98,14 +98,14 @@
 //! # extern crate inth_oauth2;
 //! # extern crate rustc_serialize;
 //! # extern crate chrono;
-//! use inth_oauth2::{TokenPair, AccessToken, RefreshToken};
+//! use inth_oauth2::{TokenPair, AccessTokenType, AccessToken, RefreshToken};
 //! use rustc_serialize::json;
 //! # use chrono::{UTC, Timelike};
 //! # fn main() {
 //! # let token_pair = TokenPair {
 //! #     access: AccessToken {
 //! #         token: String::from("AAAAAAAA"),
-//! #         token_type: String::from("bearer"),
+//! #         token_type: AccessTokenType::Bearer,
 //! #         expires: Some(UTC::now().with_nanosecond(0).unwrap()),
 //! #         scope: None,
 //! #     },
@@ -126,7 +126,7 @@ extern crate url;
 pub use client::Client;
 pub mod client;
 
-pub use token::{TokenPair, AccessToken, RefreshToken};
+pub use token::{TokenPair, AccessTokenType, AccessToken, RefreshToken};
 pub mod token;
 
 pub use error::{Error, Result};
diff --git a/src/token.rs b/src/token.rs
index 58a8dcf..e9296f6 100644
--- a/src/token.rs
+++ b/src/token.rs
@@ -12,6 +12,20 @@ pub struct TokenPair {
     pub refresh: Option<RefreshToken>,
 }
 
+/// OAuth 2.0 access token type.
+///
+/// See [RFC6749 section 7.1](http://tools.ietf.org/html/rfc6749#section-7.1).
+#[derive(Debug, Clone, PartialEq, Eq, RustcEncodable, RustcDecodable)]
+pub enum AccessTokenType {
+    /// The bearer token type.
+    ///
+    /// See [RFC6750](http://tools.ietf.org/html/rfc6750).
+    Bearer,
+
+    /// An unrecognized token type.
+    Unrecognized(String),
+}
+
 /// OAuth 2.0 access token.
 ///
 /// See [RFC6749 section 5](http://tools.ietf.org/html/rfc6749#section-5).
@@ -21,9 +35,7 @@ pub struct AccessToken {
     pub token: String,
 
     /// The type of the token issued.
-    ///
-    /// See [RFC6749 section 7.1](http://tools.ietf.org/html/rfc6749#section-7.1).
-    pub token_type: String,
+    pub token_type: AccessTokenType,
 
     /// The expiry time of the access token.
     pub expires: Option<DateTime<UTC>>,
@@ -59,7 +71,7 @@ impl Deref for TokenPair {
 #[derive(RustcEncodable, RustcDecodable)]
 struct SerializableAccessToken {
     token: String,
-    token_type: String,
+    token_type: AccessTokenType,
     expires: Option<i64>,
     scope: Option<String>,
 }