Blocking xlargescreens does not work even after changing targetSDK
===

I am developing an app for handsets. I want to block xlargeScreens, but that is only avalible for SDK level 9 or higher and I am developing for 7. I have tried solving this with this:

    <uses-sdk android:minSdkVersion="7" android:targetSdkVersion="9"/>
        <supports-screens android:xlargeScreens="false"/>

But I still get the same error that it do not find the resource. How can I fix this? (I have read all similar questions with no luck. Please do not send links.)