diff --git a/src/object.c b/src/object.c
index 4012b1e2c..6b289aa8c 100644
--- a/src/object.c
+++ b/src/object.c
@@ -646,5 +646,6 @@ MRB_API mrb_bool
 mrb_eql(mrb_state *mrb, mrb_value obj1, mrb_value obj2)
 {
   if (mrb_obj_eq(mrb, obj1, obj2)) return TRUE;
+  if (mrb_class(mrb, obj1) != mrb_class(mrb, obj2)) return FALSE;
   return mrb_test(mrb_funcall_argv(mrb, obj1, MRB_SYM_Q(eql), 1, &obj2));
 }