diff --git a/src/sage/combinat/sf/sfa.py b/src/sage/combinat/sf/sfa.py
index 3113fdb7172..1b5fcc0fe05 100644
--- a/src/sage/combinat/sf/sfa.py
+++ b/src/sage/combinat/sf/sfa.py
@@ -1673,10 +1673,14 @@ def formal_series_ring(self):
 
                 sage: type(L)
                 <class 'sage.rings.lazy_series_ring.LazySymmetricFunctions_with_category'>
+                sage: s.completion() is s.formal_series_ring()
+                True
             """
             from sage.rings.lazy_series_ring import LazySymmetricFunctions
             return LazySymmetricFunctions(self)
 
+        completion = formal_series_ring
+
 
 class FilteredSymmetricFunctionsBases(Category_realization_of_parent):
     r"""