How to exclude a folder from a nuget package

I'm using Octopack / Nuspec file to build my nuget package.

I would like to exclude certain folders which exist in the project. e.g. the "obj" file. I've been trying to get the exclude tag to work, but haven't had any luck. The nuget file builds, but the folder is still there.

Sadly, all the examples on the net specific file types and not folder.

<?xml version="1.0"?><package xmlns="http://schemas.microsoft.com/packaging/2010/07/nuspec.xsd"><metadata><id>Foo</id><title>Foo</title><version>$version$</version><authors>NA</authors><owners>NA</owners><licenseUrl>http://Foo</licenseUrl><projectUrl>http://Foo</projectUrl><requireLicenseAcceptance>false</requireLicenseAcceptance><description>Foo</description><releaseNotes>NA</releaseNotes></metadata><files><file src="obj\**\*.*" exclude="*.*" /></files></package>