diff --git a/steppyngstounes/stepper.py b/steppyngstounes/stepper.py
index 5497e7c..1545ca9 100644
--- a/steppyngstounes/stepper.py
+++ b/steppyngstounes/stepper.py
@@ -101,7 +101,7 @@ def __init__(self, start, stop, size=None, minStep=None,
         self._sizes = [size or (stop - start)]
         self._steps = [start - self._sizes[-1]]
         self._successes = [True]
-        self._values = [np.NaN]
+        self._values = [np.nan]
         self._errors = [1.]
         self._saveStep = None
         self._isDone = False