I have been using Xamnumeric editor with my Int32 fields without issue

I had to increase the size of some fields as I needed more than the max field size of an Int32, but now the editor does not bind to the field - it isn't calling the Set method of the property.

The code below works.  If I change the property to be Int64 and change ValueType="{x:Type clr:Int64}", it doesn;t work. 

Any ideas ?

<Style x:Key="Product_Eutariffcode_style" TargetType="{x:Type symphonyControls:FieldControl}">
<Setter Property="FocusVisualStyle" Value="{x:Null}"/>
<Setter Property="Focusable" Value="False"></Setter>
<Setter Property="Template">
<Setter.Value>
<ControlTemplate TargetType="{x:Type symphonyControls:FieldControl}">
<igWPF:XamNumericEditor
HorizontalAlignment="Left"
VerticalAlignment="Center"
FontSize="14"
Name="ctlProduct_Eutariffcode"
Value="{Binding Path=Eutariffcode
, Converter={StaticResource nullConverter}
,UpdateSourceTrigger=Default
,ValidatesOnDataErrors=True}"
ValueType="{x:Type clr:Int32}"
Mask="{}{char:10:0-9-}"
Validation.ErrorTemplate="{StaticResource validationTemplate}"
IsEnabled="{Binding Path=EutariffcodeIsEnabled}"
IsReadOnly="{Binding Path=EutariffcodeIsReadOnly}"
Width="120"
ToolTip="{Binding RelativeSource={RelativeSource Self},Path=(Validation.Errors), Converter={StaticResource errorConveter}}">
<i:Interaction.Behaviors>
<uiControls:SelectAllNumericEditorBehavior></uiControls:SelectAllNumericEditorBehavior>
</i:Interaction.Behaviors>
</igWPF:XamNumericEditor>
</ControlTemplate>
</Setter.Value>
</Setter>
</Style>