diff --git a/exercises/custom-set/custom_set.py b/exercises/custom-set/custom_set.py
index bfd63d81299..ee73fdbef03 100644
--- a/exercises/custom-set/custom_set.py
+++ b/exercises/custom-set/custom_set.py
@@ -23,8 +23,8 @@ def add(self, element):
     def intersection(self, other):
         pass
 
-    def difference(self, other):
+    def __sub__(self, other):
         pass
 
-    def union(self, other):
+    def __add__(self, other):
         pass