diff --git a/doc/design/scope.md b/doc/design/scope.md
index 76616cc6a64c540ec4e8fcd3e8ec94855918cb4c..cd92ba2aa86b129084acfdced14032542fbe0e79 100644
--- a/doc/design/scope.md
+++ b/doc/design/scope.md
@@ -108,7 +108,7 @@ class Scope {
 
  private:
   std::shared_ptr<Scope> parent_;
-  std::unordered_map<std::string, std::unique_ptr<Scope>> attrs_;
+  std::unordered_map<std::string, std::unique_ptr<Attribute>> attrs_;
 };
 ```
 ## Only scope can create a variable