diff --git a/src/handlers/questionnaire.lisp b/src/handlers/questionnaire.lisp
index fee7f8f..191c6dc 100644
--- a/src/handlers/questionnaire.lisp
+++ b/src/handlers/questionnaire.lisp
@@ -14,20 +14,21 @@
 (defun choose-sus-form (lang)
   "Based on LANG decide which sus form to show."
   (check-type lang string)
-  (cond ((string= lang "en") #'ml-survey/views:sus-form-en)
-        ((string= lang "de") #'ml-survey/views:sus-form-de)
-        (t (error "Unsupported language: ~A" lang))))
+  (case (string-downcase lang)
+    ("en" #'ml-survey/views:sus-form-en)
+    ("de" #'ml-survey/views:sus-form-de)
+    (otherwise (error "Unsupported language: ~A" lang))))
 
-(defun process-questionnaire-get (lang s)
+(defun process-questionnaire-get (lang survey)
   (check-type lang string)
-  (check-type s ml-survey:survey)
+  (check-type survey ml-survey:survey)
   (setf *html-lang* lang)
-  (funcall (choose-sus-form lang) (ml-survey:survey-id s)))
+  (funcall (choose-sus-form lang) (ml-survey:survey-id survey)))
 
-(defun process-questionnaire-post (request s)
+(defun process-questionnaire-post (request survey)
   (let ((post-params (post-parameters* request))
         (questionnaire-id (generate-uuid)))
-    (store-response (ensure-data-file-exist (ml-survey:survey-id s)
+    (store-response (ensure-data-file-exist (ml-survey:survey-id survey)
                                             questionnaire-id)
                     post-params)
     (ml-survey/views:questionnaire-submit)))