diff --git a/CHANGELOG.md b/CHANGELOG.md
index ab86c24c..098eabd4 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,6 +1,10 @@
 # Changelog
 
 ## Next
+### Improvements
+* Valid token presence is verified on access token creation
+* Valid tokenType presence is verified on `.revoke` calls
+
 ### Maintainance
 * Remove dev lodash library
 * Update ava test runner to v3
diff --git a/lib/access-token.js b/lib/access-token.js
index f2aa9b3a..2340bebc 100644
--- a/lib/access-token.js
+++ b/lib/access-token.js
@@ -1,6 +1,7 @@
 'use strict';
 
-const debug = require('debug')('access-token');
+const Hoek = require('@hapi/hoek');
+const debug = require('debug')('simple-oauth2:access-token');
 const isDate = require('date-fns/isDate');
 const parseISO = require('date-fns/parseISO');
 const addSeconds = require('date-fns/addSeconds');
@@ -32,49 +33,65 @@ function parseToken(token) {
   return Object.assign({}, token, tokenProperties);
 }
 
+const ACCESS_TOKEN_PROPERTY_NAME = 'access_token';
+const REFRESH_TOKEN_PROPERTY_NAME = 'refresh_token';
+
 module.exports = class AccessToken {
   static factory(config, client) {
     return (token) => new AccessToken(config, client, token);
   }
 
   constructor(config, client, token) {
+    Hoek.assert(config, 'Cannot create access token without client configuration');
+    Hoek.assert(client, 'Cannot create access token without client instance');
+    Hoek.assert(token, 'Cannot create access token without a token to parse');
+
     this.config = config;
     this.client = client;
     this.token = parseToken(token);
   }
 
   /**
-  * Check if the access token is expired or not
+  * Check if the current access token is definitely expired or not
+  *
+  * @returns {Boolean}
   */
   expired() {
     return isAfter(new Date(), this.token.expires_at);
   }
 
   /**
-  * Refresh the access token
+  * Refreshes the current access token
+  *
   * @param  {Object} params An optional argument for additional API request params.
   * @param {String|Array<String>} params.scope A String or array of strings representing the application privileges
+  * @returns {Promise<AccessToken>}
   */
   async refresh(params = {}) {
     const refreshParams = Object.assign({}, params, {
       refresh_token: this.token.refresh_token,
     });
 
-    const parameters = GrantParams.forGrant('refresh_token', refreshParams);
+    const parameters = GrantParams.forGrant(REFRESH_TOKEN_PROPERTY_NAME, refreshParams);
     const response = await this.client.request(this.config.auth.tokenPath, parameters.toObject());
 
     return new AccessToken(this.config, this.client, response);
   }
 
   /**
-  * Revoke access or refresh token
-  * @param  {String} tokenType A string containing the type of token to revoke.
-  *                              Should be either "access_token" or "refresh_token"
+  * Revokes either the access or refresh token depending on the {tokenType} value
+  *
+  * @param  {String} tokenType A string containing the type of token to revoke (access_token or refresh_token)
+  * @returns {Promise}
   */
   async revoke(tokenType) {
-    const token = tokenType === 'access_token' ? this.token.access_token : this.token.refresh_token;
+    Hoek.assert(
+      tokenType === ACCESS_TOKEN_PROPERTY_NAME || tokenType === REFRESH_TOKEN_PROPERTY_NAME,
+      `Invalid token type. Only ${ACCESS_TOKEN_PROPERTY_NAME} or ${REFRESH_TOKEN_PROPERTY_NAME} are valid values`
+    );
+
     const options = {
-      token,
+      token: this.token[tokenType],
       token_type_hint: tokenType,
     };
 
@@ -82,10 +99,11 @@ module.exports = class AccessToken {
   }
 
   /**
-   * Revoke both the existing access and refresh tokens
+   * Revokes the current access and refresh tokens
+   * @returns {Promise}
   */
   async revokeAll() {
-    await this.revoke('access_token');
-    await this.revoke('refresh_token');
+    await this.revoke(ACCESS_TOKEN_PROPERTY_NAME);
+    await this.revoke(REFRESH_TOKEN_PROPERTY_NAME);
   }
 };
diff --git a/lib/client.js b/lib/client.js
index 5adc1e5c..25244617 100644
--- a/lib/client.js
+++ b/lib/client.js
@@ -5,12 +5,14 @@ const Wreck = require('@hapi/wreck');
 const debug = require('debug')('simple-oauth2:client');
 const RequestOptions = require('./request-options');
 
+const defaultHttpHeaders = {
+  Accept: 'application/json',
+};
+
 const defaultHttpOptions = {
   json: 'strict',
   redirects: 20,
-  headers: {
-    Accept: 'application/json',
-  },
+  headers: defaultHttpHeaders,
 };
 
 module.exports = class Client {
@@ -32,8 +34,8 @@ module.exports = class Client {
     debug('Creating request to: (POST) %s', url);
     debug('Using request options: %j', options);
 
-    const result = await this.client.post(url, options);
+    const response = await this.client.post(url, options);
 
-    return result.payload;
+    return response.payload;
   }
 };
diff --git a/test/access_token.js b/test/access_token.js
index 4f1b4c45..5ae5764e 100644
--- a/test/access_token.js
+++ b/test/access_token.js
@@ -20,6 +20,15 @@ const scopeOptions = {
   },
 };
 
+test('@create => throws an error when no token payload is provided', (t) => {
+  const config = createModuleConfig();
+  const oauth2 = oauth2Module.create(config);
+
+  t.throws(() => oauth2.accessToken.create(), {
+    message: /Cannot create access token without a token to parse/,
+  });
+});
+
 test('@create => creates a new access token instance', (t) => {
   const config = createModuleConfig();
   const oauth2 = oauth2Module.create(config);
@@ -359,6 +368,18 @@ test.serial('@revoke => performs a token revoke with a custom revoke path', asyn
   scope.done();
 });
 
+test.serial('@revoke => throws an error with an invalid tokenType option', async (t) => {
+  const config = createModuleConfig();
+  const oauth2 = oauth2Module.create(config);
+
+  const accessTokenResponse = chance.accessToken();
+  const accessToken = oauth2.accessToken.create(accessTokenResponse);
+
+  await t.throwsAsync(() => accessToken.revoke('invalid_value'), {
+    message: /Invalid token type. Only access_token or refresh_token are valid values/,
+  });
+});
+
 test.serial('@revokeAll => revokes both the access and refresh tokens', async (t) => {
   const config = createModuleConfig();
   const oauth2 = oauth2Module.create(config);