diff --git a/CHANGELOG.md b/CHANGELOG.md
index b181f60..b251dbf 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,5 +1,9 @@
 # Change Log
 
+### Fixed
+* Fix defining object finalizer in Ruby 3.1 to reference a UUID string
+  by Vadim Kononov(@vkononov)
+
 ## [v0.14.0] - 2020-09-12
 
 ### Added
diff --git a/lib/finite_machine/observer.rb b/lib/finite_machine/observer.rb
index 4591d57..ec31b2a 100644
--- a/lib/finite_machine/observer.rb
+++ b/lib/finite_machine/observer.rb
@@ -1,5 +1,7 @@
 # frozen_string_literal: true
 
+require "securerandom"
+
 require_relative "async_call"
 require_relative "callable"
 require_relative "hook_event"
@@ -13,20 +15,6 @@ module FiniteMachine
   class Observer < GenericDSL
     include Safety
 
-    # Clean up callback queue
-    #
-    # @api private
-    def self.cleanup_callback_queue
-      proc do
-        begin
-          if callback_queue.alive?
-            callback_queue.shutdown
-          end
-        rescue MessageQueueDeadError
-        end
-      end
-    end
-
     # The current state machine
     attr_reader :machine
 
@@ -44,11 +32,6 @@ def initialize(machine)
       @hooks   = Hooks.new
 
       @machine.subscribe(self)
-      ObjectSpace.define_finalizer(self, self.class.cleanup_callback_queue)
-    end
-
-    def callback_queue
-      @callback_queue ||= MessageQueue.new
     end
 
     # Evaluate in current context
@@ -204,6 +187,35 @@ def defer(callable, trans_event, *data)
       callback_queue << async_call
     end
 
+    # Get an existing callback queue or create a new one
+    #
+    # @return [FiniteMachine::MessageQueue]
+    #
+    # @api private
+    def callback_queue
+      @callback_queue ||= MessageQueue.new.tap do
+        @queue_id = SecureRandom.uuid
+        ObjectSpace.define_finalizer(@queue_id, proc do
+          cleanup_callback_queue
+        end)
+      end
+    end
+
+    # Clean up the callback queue
+    #
+    # @return [Boolean, nil]
+    #
+    # @api private
+    def cleanup_callback_queue
+      ObjectSpace.undefine_finalizer(@queue_id) if @queue_id
+      return unless @callback_queue && callback_queue.alive?
+
+      begin
+        callback_queue.shutdown
+      rescue MessageQueueDeadError
+      end
+    end
+
     # Create callable instance
     #
     # @api private