diff --git a/src/Microsoft.ML.Data/Transforms/KeyToValue.cs b/src/Microsoft.ML.Data/Transforms/KeyToValue.cs
index c1863a32cf..166f14f3eb 100644
--- a/src/Microsoft.ML.Data/Transforms/KeyToValue.cs
+++ b/src/Microsoft.ML.Data/Transforms/KeyToValue.cs
@@ -510,20 +510,40 @@ public override bool SaveOnnx(OnnxContext ctx, string srcVariableName, string ds
                     var t = InternalDataKindExtensions.ToInternalDataKind(DataKind.Int64).ToType();
                     castNode.AddAttribute("to", t);
 
+                    var labelEncoderOutput = dstVariableName;
+                    var labelEncoderInput = srcVariableName;
+                    if (TypeOutput == NumberDataViewType.Double || TypeOutput == NumberDataViewType.Int64)
+                        labelEncoderOutput = ctx.AddIntermediateVariable(TypeOutput, "CastNodeOutput", true);
+
                     opType = "LabelEncoder";
-                    var node = ctx.CreateNode(opType, castNodeOutput, dstVariableName, ctx.GetNodeName(opType));
+                    var node = ctx.CreateNode(opType, castNodeOutput, labelEncoderOutput, ctx.GetNodeName(opType));
                     var keys = Array.ConvertAll<int, long>(Enumerable.Range(1, _values.Length).ToArray(), item => Convert.ToInt64(item));
                     node.AddAttribute("keys_int64s", keys);
 
                     if (TypeOutput == NumberDataViewType.Int64)
                     {
-                        long[] values = Array.ConvertAll<TValue, long>(_values.GetValues().ToArray(), item => Convert.ToInt64(item));
-                        node.AddAttribute("values_int64s", values);
+                        // LabelEncoder doesn't support mapping int64 -> int64, so values are converted to strings and later cast back to Int64s
+                        string[] values = Array.ConvertAll<TValue, string>(_values.GetValues().ToArray(), item => Convert.ToString(item));
+                        node.AddAttribute("values_strings", values);
+                        opType = "Cast";
+                        castNode = ctx.CreateNode(opType, labelEncoderOutput, dstVariableName, ctx.GetNodeName(opType), "");
+                        t = InternalDataKindExtensions.ToInternalDataKind(DataKind.Int64).ToType();
+                        castNode.AddAttribute("to", t);
+                    }
+                    else if (TypeOutput == NumberDataViewType.Single)
+                    {
+                        float[] values = Array.ConvertAll<TValue, float>(_values.GetValues().ToArray(), item => Convert.ToSingle(item));
+                        node.AddAttribute("values_floats", values);
                     }
-                    else if (TypeOutput == NumberDataViewType.Double || TypeOutput == NumberDataViewType.Single)
+                    else if (TypeOutput == NumberDataViewType.Double)
                     {
+                        // LabelEncoder doesn't support double tensors, so values are converted to floats and later cast back to doubles
                         float[] values = Array.ConvertAll<TValue, float>(_values.GetValues().ToArray(), item => Convert.ToSingle(item));
                         node.AddAttribute("values_floats", values);
+                        opType = "Cast";
+                        castNode = ctx.CreateNode(opType, labelEncoderOutput, dstVariableName, ctx.GetNodeName(opType), "");
+                        t = InternalDataKindExtensions.ToInternalDataKind(DataKind.Double).ToType();
+                        castNode.AddAttribute("to", t);
                     }
                     else if (TypeOutput == TextDataViewType.Instance)
                     {
diff --git a/src/Microsoft.ML.Data/Transforms/ValueToKeyMappingTransformer.cs b/src/Microsoft.ML.Data/Transforms/ValueToKeyMappingTransformer.cs
index 4f39d5af0b..f8cea9e8af 100644
--- a/src/Microsoft.ML.Data/Transforms/ValueToKeyMappingTransformer.cs
+++ b/src/Microsoft.ML.Data/Transforms/ValueToKeyMappingTransformer.cs
@@ -803,6 +803,7 @@ private bool SaveAsOnnxCore(OnnxContext ctx, int iinfo, ColInfo info, string src
                 }
                 else if (info.TypeSrc.GetItemType().Equals(NumberDataViewType.Double))
                 {
+                    // LabelEncoder doesn't support double tensors, so values are cast to floats
                     var castOutput = ctx.AddIntermediateVariable(null, "castOutput", true);
                     castNode = ctx.CreateNode("Cast", srcVariableName, castOutput, ctx.GetNodeName(opType), "");
                     var t = InternalDataKindExtensions.ToInternalDataKind(DataKind.Single).ToType();
@@ -813,6 +814,7 @@ private bool SaveAsOnnxCore(OnnxContext ctx, int iinfo, ColInfo info, string src
                 }
                 else if (info.TypeSrc.GetItemType().Equals(NumberDataViewType.Int64))
                 {
+                    // LabelEncoder doesn't support mapping int64 -> int64, so values are cast to strings
                     var castOutput = ctx.AddIntermediateVariable(null, "castOutput", true);
                     castNode = ctx.CreateNode("Cast", srcVariableName, castOutput, ctx.GetNodeName(opType), "");
                     var t = InternalDataKindExtensions.ToInternalDataKind(DataKind.String).ToType();
diff --git a/test/Microsoft.ML.Tests/OnnxConversionTest.cs b/test/Microsoft.ML.Tests/OnnxConversionTest.cs
index 7fd42545fb..e965be2f6a 100644
--- a/test/Microsoft.ML.Tests/OnnxConversionTest.cs
+++ b/test/Microsoft.ML.Tests/OnnxConversionTest.cs
@@ -1095,7 +1095,7 @@ public void IndicateMissingValuesOnnxConversionTest()
         [InlineData(DataKind.Int64)]
         [InlineData(DataKind.Double)]
         [InlineData(DataKind.String)]
-        public void ValueToKeyMappingOnnxConversionTest(DataKind valueType)
+        public void ValueToKeyandKeyToValueMappingOnnxConversionTest(DataKind valueType)
         {
             var mlContext = new MLContext(seed: 1);
             string filePath = GetDataPath("type-conversion.txt");
@@ -1106,7 +1106,8 @@ public void ValueToKeyMappingOnnxConversionTest(DataKind valueType)
             };
             var dataView = mlContext.Data.LoadFromTextFile(filePath, columns);
 
-            var pipeline = mlContext.Transforms.Conversion.MapValueToKey("Key", "Value");
+            var pipeline = mlContext.Transforms.Conversion.MapValueToKey("Key", "Value").
+                Append(mlContext.Transforms.Conversion.MapKeyToValue("ValueOutput", "Key"));
             var model = pipeline.Fit(dataView);
             var mlnetResult = model.Transform(dataView);
 
@@ -1123,9 +1124,9 @@ public void ValueToKeyMappingOnnxConversionTest(DataKind valueType)
                 var onnxTransformer = onnxEstimator.Fit(dataView);
                 var onnxResult = onnxTransformer.Transform(dataView);
 
-                CompareSelectedVectorColumns<UInt32>(model.ColumnPairs[0].outputColumnName, outputNames[1], mlnetResult, onnxResult);
+                CompareResults(mlnetResult.Schema[2].Name, outputNames[2], mlnetResult, onnxResult); //compare output values
+                CompareSelectedVectorColumns<UInt32>(mlnetResult.Schema[1].Name, outputNames[1], mlnetResult, onnxResult); //compare keys
             }
-
             Done();
         }
 
@@ -1555,6 +1556,8 @@ private void CompareResults(string leftColumnName, string rightColumnName, IData
                 CompareSelectedR4VectorColumns(leftColumnName, rightColumnName, left, right);
             else if (leftType == NumberDataViewType.Double)
                 CompareSelectedVectorColumns<double>(leftColumnName, rightColumnName, left, right);
+            else if (leftType == TextDataViewType.Instance)
+                CompareSelectedVectorColumns<ReadOnlyMemory<char>>(leftColumnName, rightColumnName, left, right);
         }
 
         private void CompareSelectedVectorColumns<T>(string leftColumnName, string rightColumnName, IDataView left, IDataView right)