diff --git a/libcxx/include/sstream b/libcxx/include/sstream
--- a/libcxx/include/sstream
+++ b/libcxx/include/sstream
@@ -420,10 +420,9 @@
         this->__pbump(__nout);
     }
     __hm_ = __hm == -1 ? nullptr : __p + __hm;
-    __p = const_cast<char_type*>(__rhs.__str_.data());
-    __rhs.setg(__p, __p, __p);
-    __rhs.setp(__p, __p);
-    __rhs.__hm_ = __p;
+    __rhs.setg(nullptr, nullptr, nullptr);
+    __rhs.setp(nullptr, nullptr);
+    __rhs.__hm_ = nullptr;
     this->pubimbue(__rhs.getloc());
 }
 
@@ -467,10 +466,9 @@
 
     __hm_ = __hm == -1 ? nullptr : __p + __hm;
     __mode_ = __rhs.__mode_;
-    __p = const_cast<char_type*>(__rhs.__str_.data());
-    __rhs.setg(__p, __p, __p);
-    __rhs.setp(__p, __p);
-    __rhs.__hm_ = __p;
+    __rhs.setg(nullptr, nullptr, nullptr);
+    __rhs.setp(nullptr, nullptr);
+    __rhs.__hm_ = nullptr;
     this->pubimbue(__rhs.getloc());
     return *this;
 }