diff --git a/app/helpers/reactjs_helper.rb b/app/helpers/reactjs_helper.rb
index af2bedbcdccb..f9c04ab8a6d1 100644
--- a/app/helpers/reactjs_helper.rb
+++ b/app/helpers/reactjs_helper.rb
@@ -22,6 +22,7 @@ def webpacked_plugins_with_global_js
 
   def webpacked_plugins_css_for(*plugin_names)
     Foreman::Deprecation.deprecation_warning('3.12', '`webpacked_plugins_css_for` is deprecated, plugin css is already loaded.')
+    nil
   end
 
   def read_webpack_manifest