diff --git a/common/python/nomadcore/json_support.py b/common/python/nomadcore/json_support.py
index 724a7f21b6fcf7a80f658b683e02b03d4c13e518..9679a62615beebb5c0f7dd8a912f50b176658831 100644
--- a/common/python/nomadcore/json_support.py
+++ b/common/python/nomadcore/json_support.py
@@ -1,16 +1,17 @@
 from builtins import object
 import json
 from nomadcore.compact_sha import sha512
+import numpy
 
 """Various functions to simplify and standardize dumping objects to json"""
 
 def numpyEncoder(o):
     """new default function for json class so that numpy arrays and sets can be encoded"""
     # check if object is a numpy array
-    if isinstance(o, np.ndarray):
+    if isinstance(o, numpy.ndarray):
         # ensure that we have an array with row-major memory order (C like)
         if not o.flags['C_CONTIGUOUS']:
-            o = np.ascontiguousarray(o)
+            o = numpy.ascontiguousarray(o)
         return o.tolist()
         # see default method in python/json/encoder.py
     elif isinstance(o, set):