diff --git a/datasets/raise/utils.py b/datasets/raise/utils.py
index d2586c7..258c80a 100644
--- a/datasets/raise/utils.py
+++ b/datasets/raise/utils.py
@@ -27,7 +27,7 @@ def denoise(imageNpArray, denoiserName):
     return imageDenoisedNpArray
 
 class iterativeMean:
-    mean = 0
+    mean = None
     numberOfElementsInMean = 0
 
     def add(self, element):