diff --git a/mrbgems/mruby-io/mrblib/io.rb b/mrbgems/mruby-io/mrblib/io.rb
index 8cd442ac0..d5307016b 100644
--- a/mrbgems/mruby-io/mrblib/io.rb
+++ b/mrbgems/mruby-io/mrblib/io.rb
@@ -210,7 +210,7 @@ class IO
   #
   # 15.2.20.5.3
   def each(&block)
-    return to_enum unless block
+    return to_enum(:each) unless block
 
     while line = self.gets
       block.call(line)