diff --git a/app/lib/activitypub/case_transform.rb b/app/lib/activitypub/case_transform.rb
index 7f716f8624..ef0c6e1f91 100644
--- a/app/lib/activitypub/case_transform.rb
+++ b/app/lib/activitypub/case_transform.rb
@@ -14,6 +14,8 @@ module ActivityPub::CaseTransform
       when String
         camel_lower_cache[value] ||= if value.start_with?('_:')
                                        '_:' + value.gsub(/\A_:/, '').underscore.camelize(:lower)
+                                     elsif value.start_with?('_')
+                                       value
                                      else
                                        value.underscore.camelize(:lower)
                                      end