Created Unassigned: ValuRangeTextBox problem setting MinValue and MaxValue [22151]

I'm trying to use a RangeTextBox with Min and MaxValue with this code :

NameSpaces :
```
xmlns:sys="clr-namespace:System;assembly=mscorlib"
xmlns:xcdg="http://schemas.xceed.com/wpf/xaml/datagrid"
xmlns:xctk="http://schemas.xceed.com/wpf/xaml/toolkit"
```

in my XAML :
```
<xctk:ValueRangeTextBox ValueDataType="{x:Type sys:Int32}" MinValue="0" MaxValue="1000" Margin="30,26,0,0" />
```
I get the following error : The value is not of type Int32, parameter name MinValue. Same for MaxValue.

Thanks for any help.