diff --git a/mrbgems/mruby-data/src/data.c b/mrbgems/mruby-data/src/data.c
index f25dc88d1..413c892d8 100644
--- a/mrbgems/mruby-data/src/data.c
+++ b/mrbgems/mruby-data/src/data.c
@@ -96,6 +96,10 @@ mrb_data_members(mrb_state *mrb, mrb_value obj)
 static mrb_value
 mrb_data_ref(mrb_state *mrb, mrb_value obj)
 {
+  mrb_int argc = mrb_get_argc(mrb);
+  if (argc != 0) {
+    mrb_argnum_error(mrb, argc, 0, 0);
+  }
   mrb_int i = mrb_integer(mrb_proc_cfunc_env_get(mrb, 0));
   mrb_value *ptr = RDATA_PTR(obj);