diff --git a/book/en-us/03-runtime.md b/book/en-us/03-runtime.md
index 907c112e..878c127c 100644
--- a/book/en-us/03-runtime.md
+++ b/book/en-us/03-runtime.md
@@ -345,7 +345,7 @@ int main()
 
     const std::string& lv2 = lv1 + lv1; // legal, const lvalue reference can extend temp variable's lifecycle
     // lv2 += "Test";                   // illegal, const ref can't be modified
-    std::cout << lv2 << std::endl;      // string,string
+    std::cout << lv2 << std::endl;      // string,string,
 
     std::string&& rv2 = lv1 + lv2;      // legal, rvalue ref extend lifecycle
     rv2 += "string";                    // legal, non-const reference can be modified
diff --git a/book/zh-cn/03-runtime.md b/book/zh-cn/03-runtime.md
index debfd6e2..3738bc1a 100644
--- a/book/zh-cn/03-runtime.md
+++ b/book/zh-cn/03-runtime.md
@@ -293,7 +293,7 @@ int main()
 
     const std::string& lv2 = lv1 + lv1; // 合法, 常量左值引用能够延长临时变量的生命周期
     // lv2 += "Test"; // 非法, 常量引用无法被修改
-    std::cout << lv2 << std::endl; // string,string
+    std::cout << lv2 << std::endl; // string,string,
 
     std::string&& rv2 = lv1 + lv2; // 合法, 右值引用延长临时对象生命周期
     rv2 += "Test"; // 合法, 非常量引用能够修改临时变量