diff --git a/nifty5/minimization/metric_gaussian_kl_mpi.py b/nifty5/minimization/metric_gaussian_kl_mpi.py
index 8111db043cd15e68316da8f499aed1615b9ba09d..1970bb2e00cbd10858823acfce04c389a98ea632 100644
--- a/nifty5/minimization/metric_gaussian_kl_mpi.py
+++ b/nifty5/minimization/metric_gaussian_kl_mpi.py
@@ -40,6 +40,7 @@ def _shareRange(nwork, nshares, myshare):
 
 
 def np_allreduce_sum(arr):
+    arr = np.array(arr)
     res = np.empty_like(arr)
     _comm.Allreduce(arr, res, MPI.SUM)
     return res