diff --git a/monai/transforms/utility/dictionary.py b/monai/transforms/utility/dictionary.py
index 7333484d13..0a4df58647 100644
--- a/monai/transforms/utility/dictionary.py
+++ b/monai/transforms/utility/dictionary.py
@@ -1165,6 +1165,8 @@ class ClassesToIndicesd(MapTransform):
 
     """
 
+    backend = ClassesToIndices.backend
+
     def __init__(
         self,
         keys: KeysCollection,