I cannot figure out why HeaderText or validation controls always fallback to default culture - even though rest of the controls are in correct culture.

I have a gridView with HeaderText specified in this way>

 <asp:BoundField DataField="totalSales" HeaderText="<%$ Resources:Strings,TotalSales %>" />

In the same way I have validation controls and they can't be localized.

Only this syntax does work > <%= Resources.Strings.Payments %>

I set different culture in Master page using this statement in Page_Init

Me.Page.Culture = "pl-PL"
 Me.Page.UICulture = "pl-PL"

Can anyone spot what's wrong? I have been Googling it for last few days without success.

Thanks!