diff --git a/Cattery/Calico/OMS/StefCal/GainDiagPhase.py b/Cattery/Calico/OMS/StefCal/GainDiagPhase.py
index 6b6f186..b076f0a 100644
--- a/Cattery/Calico/OMS/StefCal/GainDiagPhase.py
+++ b/Cattery/Calico/OMS/StefCal/GainDiagPhase.py
@@ -201,7 +201,7 @@ def iterate (self,lhs,rhs,bitflags,bounds=None,verbose=0,niter=0,weight=None):
           print "S%d %s:%s"%(step,p,i),"G''",g1[p,i],g1[p,i][verbose_element];
         # take difference at second step
         gaindiff2[p] += square(gnew - gold)
-        gaindiff2[p][pmask] = 0;
+        gaindiff2[p][mask] = 0;
         # apply solution averaging
         if self.opts.average == 1 or (self.opts.average == 2 and step):
           gnew += gold;