diff --git a/libcxx/include/string b/libcxx/include/string
--- a/libcxx/include/string
+++ b/libcxx/include/string
@@ -2260,7 +2260,14 @@
     if (this != &__str)
     {
         __copy_assign_alloc(__str);
-        return assign(__str.data(), __str.size());
+        if (__str.__is_long()) {
+            return assign(__str.data(), __str.size());
+        }
+        if (__is_long()) {
+            __alloc_traits::deallocate(__alloc(), __get_long_pointer(),
+                                       __get_long_cap());
+        }
+        __r_.first().__r = __str.__r_.first().__r;
     }
     return *this;
 }