diff --git a/nifty4/data_objects/distributed_do.py b/nifty4/data_objects/distributed_do.py
index c18d438793e2783ce0b52055f69c5aa24695e3af..14d132d36ef0df546dfb09a2f9d8fbef28377ddf 100644
--- a/nifty4/data_objects/distributed_do.py
+++ b/nifty4/data_objects/distributed_do.py
@@ -20,6 +20,7 @@ import numpy as np
 from .random import Random
 from mpi4py import MPI
 import sys
+from functools import reduce
 
 _comm = MPI.COMM_WORLD
 ntask = _comm.Get_size()