diff --git a/CppCoreGuidelines.md b/CppCoreGuidelines.md
index a81e4e4..1d34c5f 100644
--- a/CppCoreGuidelines.md
+++ b/CppCoreGuidelines.md
@@ -4701,7 +4701,7 @@ Users will be surprised if copy/move construction and copy/move assignment do lo
         };
         shared_ptr<Impl> p;
     public:
-        Silly(const Silly& a) : p{a.p} { *p = *a.p; }   // deep copy
+        Silly(const Silly& a) : p(make_shared<Impl>()) { *p = *a.p; }   // deep copy
         Silly& operator=(const Silly& a) { p = a.p; }   // shallow copy
         // ...
     };