SQLDataSource SQLCacheDependency with MSSQL 2008 R2

Running: ASP.NET ver. 4.5. MSSQL 2008 R2

I'm trying to get caching with SQL dependency working on a SQLDataSource control. However, I get the following error in runtime:

The database 'IM' is not enabled for SQL cache notification.

To enable a database for SQL cache notification, please use the System.Web.Caching.SqlCacheDependencyAdmin.EnableNotifications method, or the command line tool aspnet_regsql. To use the tool, please run 'aspnet_regsql.exe -?' for more information.

My confusion is that I believe cache notifications were discontinued after 2005 and replaced with a new service in 2008 R2. Is this correct? If so, what do I need to do to allow for caching with dependency out of the SQLDataSource?

Code for the SQLDataSource:

<asp:SqlDataSource ID="custItemsDS" runat="server" ConnectionString="<%$ ConnectionStrings:IMConnectionString %>" SelectCommand="...select command..." UpdateCommand="...update command..." EnableCaching="True" SqlCacheDependency="IM:ct_CustItem">
                ...parameters...
</asp:SqlDataSource>

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Web.config

  <system.web>
    <caching>
      <sqlCacheDependency enabled="true">
        <databases>
          <add connectionStringName="IMConnectionString" name="IM" pollTime="1000"/>
        </databases>
      </sqlCacheDependency>
    </caching>

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Thank you in advance for your help!