diff --git a/lib/timeout.rb b/lib/timeout.rb
index ee24349a3e..e7b11c0a86 100644
--- a/lib/timeout.rb
+++ b/lib/timeout.rb
@@ -85,7 +85,7 @@ module Timeout
 
     message ||= "execution expired".freeze
 
-    if (scheduler = Fiber.current_scheduler)&.respond_to?(:timeout_after)
+    if Fiber.respond_to?(:current_scheduler) && (scheduler = Fiber.current_scheduler)&.respond_to?(:timeout_after)
       return scheduler.timeout_after(sec, klass || Error, message, &block)
     end