diff --git a/src/daglib/set.py b/src/daglib/set.py
index 182a427..6fb2ff9 100644
--- a/src/daglib/set.py
+++ b/src/daglib/set.py
@@ -45,10 +45,10 @@ class DAGSetView(MutableSet[T]):
 
     def __iadd__(self, other: Iterable[T]) -> DAGSetView[T]:
         # a += b => update/extend
-        self |= ensure_set(other)
-        return self
+        return super().__ior__(ensure_set(other))
 
     def __ior__(self, other: Iterable[T]) -> DAGSetView[T]:
+        # a |= b => update/extend
         return super().__ior__(ensure_set(other))
 
     def __isub__(self, other: Iterable[T]) -> DAGSetView[T]: