diff --git a/types/index.d.ts b/types/index.d.ts
index b6a073b5..51c43134 100644
--- a/types/index.d.ts
+++ b/types/index.d.ts
@@ -74,10 +74,10 @@ export class DropboxAuth {
    * @arg {boolean} [usePKCE] - Whether or not to use Sha256 based PKCE. PKCE should be only use on
    * client apps which doesn't call your server. It is less secure than non-PKCE flow but
    * can be used if you are unable to safely retrieve your app secret
-   * @returns {Promise<String>} - Url to send user to for Dropbox API authentication
+   * @returns {Promise<string>} - Url to send user to for Dropbox API authentication
    * returned in a promise
    */
-  getAuthenticationUrl(redirectUri: string, state?: string, authType?: 'token' | 'code', tokenAccessType?: null | 'legacy' | 'offline' | 'online', scope?: Array<String>, includeGrantedScopes?: 'none' | 'user' | 'team', usePKCE?: boolean): Promise<String>;
+  getAuthenticationUrl(redirectUri: string, state?: string, authType?: 'token' | 'code', tokenAccessType?: null | 'legacy' | 'offline' | 'online', scope?: Array<string>, includeGrantedScopes?: 'none' | 'user' | 'team', usePKCE?: boolean): Promise<string>;
 
   /**
    * Get the client id