Cannot find resource inside TabControl

Question

I have this TabControl

    <TabControl
        x:Name="TabControl"
        ItemTemplate="{StaticResource MyTemplate}">
        <TabControl.Resources>
            <DataTemplate x:Key="MyTemplate">
                <TextBlock
                    Width="80"
                    Height="25"
                    FontWeight="Bold"
                    Text="{Binding Header}" />
            </DataTemplate>
            <DataTemplate DataType="{x:Type objects:LivingBeing}">
                ...
            </DataTemplate>
            <DataTemplate DataType="{x:Type objects:Thing}">
                ...
            </DataTemplate>
        </TabControl.Resources>
    </TabControl>

I set TabControl.ItemsSource = list; and The parent of each object in this list has Header variable and I want to programmatically set the title of each tab but it gives me error: "Cannot find resource named 'MyTemplate'. Resource names are case sensitive."

But the spelling is correct, how to fix this please?