Control from WPFToolkit doesn't exist in namespace

I added to references WPFToolkit.dll and I added do my .xaml file following line:

xmlns:toolkit="clr-namespace:Microsoft.Windows.Controls;assembly=WpfToolkit"

and before following line:

xmlns:toolkit="http://schemas.microsoft.com/wpf/2008/toolkit"

In both cases in line

<toolkit:NumericUpDown Value="10" Increment="1" Maximum="10" Minimum="0" />

I have error:

Error 1 The tag 'NumericUpDown' does not exist in XML namespace 'http://schemas.microsoft.com/wpf/2008/toolkit'. Line 20 Position 18. C:\Users\Diament\Documents\Visual Studio 2008\Projects\MyBasicFlyffKeystroke\MyBasicFlyffKeystroke\Window.xaml 20 18 MyBasicFlyffKeystroke

Where is the problem? :(