diff --git a/Code/Mantid/Framework/CurveFitting/src/NormaliseByPeakArea.cpp b/Code/Mantid/Framework/CurveFitting/src/NormaliseByPeakArea.cpp
index 703f3c15ffb8..96fe876b8fc3 100644
--- a/Code/Mantid/Framework/CurveFitting/src/NormaliseByPeakArea.cpp
+++ b/Code/Mantid/Framework/CurveFitting/src/NormaliseByPeakArea.cpp
@@ -368,6 +368,7 @@ namespace Mantid
                 double invE2 = 1/(ek*ek);
                 yout /= eout*eout;
                 yout += yk*invE2;
+                double wt = (1/(eout*eout)) + invE2;
                 yout /= wt;
                 eout = sqrt(1/wt);
               }