diff --git a/app/helpers/application_helper.rb b/app/helpers/application_helper.rb
index 5e0f736ddcd37ffa22146a6c21274b37a1176ba4..c234968c2a06679af775c7f5db52ee3e47b76f45 100644
--- a/app/helpers/application_helper.rb
+++ b/app/helpers/application_helper.rb
@@ -51,7 +51,9 @@ module ApplicationHelper
   end
 
   def masked_string(string)
-    string.gsub(/.+(?=.{5})/, '•' * (string.length - 5))
+    string = string.to_s # in case it was nil
+    mask_length = [(string.length - 5), 0].max
+    string.to_s.gsub(/.+(?=.{5})/, '•' * mask_length)
   end
 
   def language_name(iso_code)