diff --git a/lib/oauth/authenticator.js b/lib/oauth/authenticator.js
index 0811312b..8d3c88c9 100644
--- a/lib/oauth/authenticator.js
+++ b/lib/oauth/authenticator.js
@@ -2,6 +2,7 @@
 
 var ApiAuthRequestError = require('../error/ApiAuthRequestError');
 var JwtAuthenticator = require('../jwt/jwt-authenticator');
+var ScopeFactoryAuthenticator = require('../oauth/scope-factory-authenticator');
 var OAuthPasswordGrantRequestAuthenticator = require('../oauth/password-grant').authenticator;
 var OAuthRefreshTokenGrantRequestAuthenticator = require('../oauth/refresh-grant').authenticator;
 var OAuthIdSiteTokenGrantAuthenticator = require('../oauth/id-site-grant').authenticator;
@@ -85,7 +86,7 @@ OAuthAuthenticator.prototype.authenticate = function authenticate(req, callback)
     }
   }
 
-  if (this.scopeFactory && typeof authenticator.setScopeFactory === 'function') {
+  if (this.scopeFactory && (authenticator instanceof ScopeFactoryAuthenticator)) {
     if (!this.signingKey) {
       callback(new ApiAuthRequestError({
         userMessage: 'Invalid Request',