diff --git a/src/Microsoft.ML.Fairlearn/Reductions/UtilityParity.cs b/src/Microsoft.ML.Fairlearn/Reductions/UtilityParity.cs
index be304962ce..0da2683d55 100644
--- a/src/Microsoft.ML.Fairlearn/Reductions/UtilityParity.cs
+++ b/src/Microsoft.ML.Fairlearn/Reductions/UtilityParity.cs
@@ -122,7 +122,7 @@ public override DataFrame Gamma(PrimitiveDataFrameColumn<float> yPred/* Maybe ch
             dfNeg["sign"].FillNulls("-", inPlace: true);
 
             // stack the temp dataframe dfNeg to the bottom dataframe that we want to return
-            dfNeg.Rows.ToList<DataFrameRow>().ForEach(row => { gSigned.Append(row, inPlace: true); });
+            gSigned.Append(dfNeg.Rows, inPlace: true);
 
             return gSigned;
         }