diff --git a/mrbgems/mruby-objectspace/src/mruby_objectspace.c b/mrbgems/mruby-objectspace/src/mruby_objectspace.c
index d8ce19e82..1b293f019 100644
--- a/mrbgems/mruby-objectspace/src/mruby_objectspace.c
+++ b/mrbgems/mruby-objectspace/src/mruby_objectspace.c
@@ -112,9 +112,9 @@ os_count_objects(mrb_state *mrb, mrb_value self)
 }
 
 struct os_each_object_data {
-  mrb_value block;
   struct RClass *target_module;
   mrb_int count;
+  mrb_value block;
 };
 
 static int