diff --git a/lib/irb/cmd/fork.rb b/lib/irb/cmd/fork.rb
index ae4d51b5d1..31d53dcaba 100644
--- a/lib/irb/cmd/fork.rb
+++ b/lib/irb/cmd/fork.rb
@@ -21,7 +21,7 @@ module IRB
           class << self
             alias_method :exit, ExtendCommand.irb_original_method_name('exit')
           end
-          if iterator?
+          if block_given?
             begin
               yield
             ensure