compression of ico image failing on iis 7.5

Question

240.6 KB total in compressible text, target size = 238.2 KB - potential savings = 2.4 KB

FAILED - (3.2 KB, compressed = 0.8 KB - savings of 2.4 KB) - https://www.domain.com/favicon.ico

I have the following markup in the web.config, but it does not seem to help:

 <httpCompression directory="%SystemDrive%\inetpub\temp\IIS Temporary
 Compressed Files">
      <scheme name="gzip" dll="%Windir%\system32\inetsrv\gzip.dll" />
        <staticTypes>
           <add mimeType="image/x-icon" enabled="true" />
        </staticTypes>
</httpCompression>