diff --git a/lib/live/definable.rb b/lib/live/definable.rb
index aa1f6e8..daca760 100644
--- a/lib/live/definable.rb
+++ b/lib/live/definable.rb
@@ -1,7 +1,6 @@
 require 'dotenv'
 
-# FIXME: do not use global variable
-$definable_thread_group ||= ThreadGroup.new
+DEFINABLE_THREAD_GROUP ||= ThreadGroup.new # rubocop:disable Lint/OrAssignmentToConstant
 
 module Live
   # offers typed constant defintions with default value, by using lots of introspecting...
@@ -85,13 +84,13 @@ module Live
       value = typed_value(type, raw_value, default)
       definitions[constant] = { type:, default:, value: }
 
-      # puts("-- new definition #{constant}:#{definitions[constant]}")
+      # logger.debug("new definition #{constant}:#{definitions[constant]}")
       value
     end
 
     def start_listener
-      $definable_thread_group.list.each(&:kill)
-      $definable_thread_group.add(Thread.new do
+      DEFINABLE_THREAD_GROUP.list.each(&:kill)
+      DEFINABLE_THREAD_GROUP.add(Thread.new do
         listener = Listen.to(Rails.root, only: /^\.env\.?/) do
           @@class_origin.reload_from_env
         rescue StandardError