diff --git a/.rubocop_todo.yml b/.rubocop_todo.yml
index d4738691e..e91e986ef 100644
--- a/.rubocop_todo.yml
+++ b/.rubocop_todo.yml
@@ -390,10 +390,6 @@ Lint/HandleExceptions:
     - 'lib/redmine/scm/adapters/cvs_adapter.rb'
     - 'lib/redmine/scm/adapters/subversion_adapter.rb'
 
-Lint/IneffectiveAccessModifier:
-  Exclude:
-    - 'app/models/auth_source_ldap.rb'
-
 Lint/InterpolationCheck:
   Exclude:
     - 'app/models/user.rb'
diff --git a/app/models/auth_source_ldap.rb b/app/models/auth_source_ldap.rb
index 3c55bff75..aba76a6fc 100644
--- a/app/models/auth_source_ldap.rb
+++ b/app/models/auth_source_ldap.rb
@@ -244,10 +244,13 @@ class AuthSourceLdap < AuthSource
     attrs
   end
 
-  def self.get_attr(entry, attr_name)
-    if !attr_name.blank?
-      value = entry[attr_name].is_a?(Array) ? entry[attr_name].first : entry[attr_name]
-      value.to_s.force_encoding('UTF-8')
+  # Singleton class method is public
+  class << self
+    def get_attr(entry, attr_name)
+      if !attr_name.blank?
+        value = entry[attr_name].is_a?(Array) ? entry[attr_name].first : entry[attr_name]
+        value.to_s.force_encoding('UTF-8')
+      end
     end
   end
 end