diff --git a/Doc/library/dataclasses.rst b/Doc/library/dataclasses.rst
index 9835c480d0ea55..e9af20a04af167 100644
--- a/Doc/library/dataclasses.rst
+++ b/Doc/library/dataclasses.rst
@@ -533,7 +533,7 @@ Mutable default values
      class C:
          x = []
          def add(self, element):
-             self.x += element
+             self.x.append(element)
 
      o1 = C()
      o2 = C()