WPF Datagridtextcolumn sorting not working on first click after setting sortmember path

Question

<DataGridTextColumn x:Name="HiddenColumn" Visibility="Hidden" Header="Make" CanUserResize="True" Binding="{Binding Make}" />
<DataGridTextColumn Header="Car" MinWidth="50" Width="150" MaxWidth="150" CanUserResize="True" Binding="{Binding car}" SortMemberPath="Make" />

without using the sort member path , the column sorts.

But when i use sortmemberpath, for the first click on the column header there is no sort, from the second click it works fine.

Both columns display string.

Strange behaviour, any help will be appreciated!