2 files changed, 17 insertions, 17 deletions
diff --git a/mrbgems/mruby-os-memsize/src/memsize.c b/mrbgems/mruby-os-memsize/src/memsize.c
index d82c6b7ed..14f90109d 100644
--- a/mrbgems/mruby-os-memsize/src/memsize.c
+++ b/mrbgems/mruby-os-memsize/src/memsize.c
@@ -44,6 +44,19 @@ os_memsize_of_method(mrb_state* mrb, mrb_value method_obj)
   return size;
 }
 
+static mrb_bool
+obj_is_kind_of_checked(mrb_state *mrb, mrb_value obj, const char *classname)
+{
+  mrb_value objclass = mrb_obj_value(mrb->object_class);
+
+  if (mrb_const_defined(mrb, objclass, mrb_intern_cstr(mrb, classname))) {
+    struct RClass *klass = mrb_class_get(mrb, classname);
+    return mrb_obj_is_kind_of(mrb, obj, klass);
+  }
+
+  return FALSE;
+}
+
 static mrb_int
 os_memsize_of_object(mrb_state* mrb, mrb_value obj)
 {
@@ -54,6 +67,7 @@ os_memsize_of_object(mrb_state* mrb, mrb_value obj)
       size += mrb_objspace_page_slot_size();
       if (!RSTR_EMBED_P(RSTRING(obj)) && !RSTR_SHARED_P(RSTRING(obj))) {
         size += RSTRING_CAPA(obj);
+        size++; /* NUL terminator */
       }
       break;
     case MRB_TT_CLASS:
@@ -66,8 +80,8 @@ os_memsize_of_object(mrb_state* mrb, mrb_value obj)
     case MRB_TT_OBJECT: {
       size += mrb_objspace_page_slot_size();
       size += os_memsize_of_ivars(mrb, obj);
-      if (mrb_obj_is_kind_of(mrb, obj, mrb_class_get(mrb, "UnboundMethod")) ||
-          mrb_obj_is_kind_of(mrb, obj, mrb_class_get(mrb, "Method"))){
+      if (obj_is_kind_of_checked(mrb, obj, "UnboundMethod") ||
+          obj_is_kind_of_checked(mrb, obj, "Method")) {
         size += os_memsize_of_method(mrb, obj);
       }
       break;
diff --git a/mrbgems/mruby-os-memsize/test/memsize.rb b/mrbgems/mruby-os-memsize/test/memsize.rb
index c6b1b7b2d..6be8f1b06 100644
--- a/mrbgems/mruby-os-memsize/test/memsize.rb
+++ b/mrbgems/mruby-os-memsize/test/memsize.rb
@@ -12,7 +12,7 @@ assert 'ObjectSpace.memsize_of' do
   assert_not_equal ObjectSpace.memsize_of('a'), 0, 'memsize of str'
 
   if __ENCODING__ == "UTF-8"
-    assert_not_equal ObjectSpace.memsize_of("縺薙ｓ縺ｫ縺｡縺ｯ荳也阜"), 0, 'memsize of utf8 str'
+    assert_not_equal ObjectSpace.memsize_of("こんにちは世界"), 0, 'memsize of utf8 str'
   end
 
   # class defs
@@ -22,20 +22,6 @@ assert 'ObjectSpace.memsize_of' do
   empty_class_def_size = ObjectSpace.memsize_of Class.new
   assert_not_equal empty_class_def_size, 0, 'Class def not zero'
 
-  class_without_methods = Class.new do
-    @a = 1
-    @b = 2
-  end
-  class_total_size = empty_class_def_size + (int_size * 2)
-  assert_equal ObjectSpace.memsize_of(class_without_methods), class_total_size, 'class without methods size'
-
-  module_without_methods = Module.new do
-    @a = 1
-    @b = 2
-  end
-  module_total_size = empty_class_def_size + (int_size * 2)
-  assert_equal ObjectSpace.memsize_of(module_without_methods), module_total_size, 'module without methods size'
-
   proc_size = ObjectSpace.memsize_of Proc.new { x = 1; x }
   assert_not_equal proc_size, 0