diff --git a/lib/rake/thread_pool.rb b/lib/rake/thread_pool.rb
index 332956670..76aa3b74b 100644
--- a/lib/rake/thread_pool.rb
+++ b/lib/rake/thread_pool.rb
@@ -1,6 +1,7 @@
 # frozen_string_literal: true
 
 require "rake/promise"
+require "set"
 
 module Rake
 
@@ -9,7 +10,6 @@ class ThreadPool # :nodoc: all
     # Creates a ThreadPool object.  The +thread_count+ parameter is the size
     # of the pool.
     def initialize(thread_count)
-      require "set"
       @max_active_threads = [thread_count, 0].max
       @threads = Set.new
       @threads_mon = Monitor.new