diff --git a/app/controllers/exercises_controller.rb b/app/controllers/exercises_controller.rb
index ccd7180a..62799e27 100644
--- a/app/controllers/exercises_controller.rb
+++ b/app/controllers/exercises_controller.rb
@@ -187,7 +187,7 @@ class ExercisesController < ApplicationController
     lti_parameters = LtiParameter.find_by(external_users_id: current_user.id,
                                           exercises_id: @exercise.id)
     if lti_parameters
-      lti_json = lti_parameters.lti_parameters[:lis_outcome_service_url]
+      lti_json = lti_parameters.lti_parameters["lis_outcome_service_url"]
       @course_token =
           if match = lti_json.match(/^.*courses\/([a-z0-9\-]+)\/sections/)
             match.captures.first