diff --git a/mrbgems/mruby-io/mrblib/io.rb b/mrbgems/mruby-io/mrblib/io.rb
index f418c4f2e..8a500f80c 100644
--- a/mrbgems/mruby-io/mrblib/io.rb
+++ b/mrbgems/mruby-io/mrblib/io.rb
@@ -107,14 +107,6 @@ class IO
     ungetc s
   end
 
-  def gets(*args)
-    begin
-      readline(*args)
-    rescue EOFError
-      nil
-    end
-  end
-
   # 15.2.20.5.3
   def each(&block)
     return to_enum unless block
diff --git a/mrbgems/mruby-io/src/io.c b/mrbgems/mruby-io/src/io.c
index ae6f43908..2998cf102 100644
--- a/mrbgems/mruby-io/src/io.c
+++ b/mrbgems/mruby-io/src/io.c
@@ -1884,7 +1884,7 @@ mrb_init_io(mrb_state *mrb)
   mrb_define_method(mrb, io, "isatty",     io_isatty,     MRB_ARGS_NONE());
   mrb_define_method(mrb, io, "eof?",       io_eof,        MRB_ARGS_NONE());   /* 15.2.20.5.6 */
   mrb_define_method(mrb, io, "getc",       io_getc,       MRB_ARGS_NONE());   /* 15.2.20.5.8 */
-  mrb_define_method(mrb, io, "gets",       io_gets,       MRB_ARGS_NONE());   /* 15.2.20.5.9 */
+  mrb_define_method(mrb, io, "gets",       io_gets,       MRB_ARGS_OPT(2));   /* 15.2.20.5.9 */
   mrb_define_method(mrb, io, "read",       io_read,       MRB_ARGS_OPT(2));   /* 15.2.20.5.14 */
   mrb_define_method(mrb, io, "readchar",   io_readchar,   MRB_ARGS_NONE());   /* 15.2.20.5.15 */
   mrb_define_method(mrb, io, "readline",   io_readline,   MRB_ARGS_OPT(2));   /* 15.2.20.5.16 */