diff --git a/scilpy/utils/metrics_tools.py b/scilpy/utils/metrics_tools.py
index 2aac75872..66860549d 100644
--- a/scilpy/utils/metrics_tools.py
+++ b/scilpy/utils/metrics_tools.py
@@ -157,7 +157,8 @@ def weighted_mean_std(weights, data):
         a tuple containing the mean and standard deviation of the data
     """
 
-    masked_data = np.ma.masked_array(data, np.logical_or(np.isnan(a), np.isinf(a)))
+    masked_data = np.ma.masked_array(data, np.logical_or(np.isnan(data),
+                                                         np.isinf(data)))
     mean = np.ma.average(masked_data, weights=weights)
     variance = np.ma.average((masked_data-mean)**2, weights=weights)