diff --git a/src/Microsoft.ML.Data/Transforms/GenerateNumberTransform.cs b/src/Microsoft.ML.Data/Transforms/GenerateNumberTransform.cs
index 1dc8ad878e..8da3554c27 100644
--- a/src/Microsoft.ML.Data/Transforms/GenerateNumberTransform.cs
+++ b/src/Microsoft.ML.Data/Transforms/GenerateNumberTransform.cs
@@ -198,7 +198,7 @@ protected override IEnumerable<KeyValuePair<string, DataViewType>> GetAnnotation
                 Contracts.Assert(0 <= iinfo & iinfo < InfoCount);
                 var items = base.GetAnnotationTypesCore(iinfo);
                 if (!UseCounter[iinfo])
-                    items.Prepend(BooleanDataViewType.Instance.GetPair(AnnotationUtils.Kinds.IsNormalized));
+                    items = items.Prepend(BooleanDataViewType.Instance.GetPair(AnnotationUtils.Kinds.IsNormalized));
                 return items;
             }
 
diff --git a/src/Microsoft.ML.TimeSeries/RootCauseAnalyzer.cs b/src/Microsoft.ML.TimeSeries/RootCauseAnalyzer.cs
index 953ee35ed1..b6ce81f181 100644
--- a/src/Microsoft.ML.TimeSeries/RootCauseAnalyzer.cs
+++ b/src/Microsoft.ML.TimeSeries/RootCauseAnalyzer.cs
@@ -146,7 +146,7 @@ private void LocalizeRootCausesByDimension(PointTree anomalyTree, PointTree poin
 
             if (best == null)
             {
-                _preparedCauses.Append(new RootCause { Items = new List<RootCauseItem>() { new RootCauseItem(anomalyDimension) } });
+                _preparedCauses.Add(new RootCause { Items = new List<RootCauseItem>() { new RootCauseItem(anomalyDimension) } });
             }
 
             bool rootAsAnomaly = false;