WiX - Trying to set the permissions of a service using util:PermissionEx and getting an Error 1

The question WiX - Install Windows Service and give permissions is exactly what I am trying to do. First I have added the UtilExtension namespace like this:

<Wix xmlns="http://schemas.microsoft.com/wix/2006/wi"
     xmlns:util="http://schemas.microsoft.com/wix/UtilExtension">

Then I have added the following to the ServiceInstall element:

<util:PermissionEx
              User="Authenticated Users"
              GenericAll="yes"
              ServiceChangeConfig="yes"
              ServiceEnumerateDependents="yes"
              ChangePermission="yes"
              ServiceInterrogate="yes"
              ServicePauseContinue="yes"
              ServiceQueryConfig="yes"
              ServiceQueryStatus="yes"
              ServiceStart="yes"
              ServiceStop="yes" />

Finally the compiler provides me with the following error message:

Error 1 The ServiceInstall element contains an unhandled extension element 'util:PermissionEx'. Please ensure that the extension for elements in the 'http://schemas.microsoft.com/wix/UtilExtension' namespace has been provided.

Is there something else I need to do to ensure the extension for the elements has been provided? How do I fix this?

You need to add the reference to the WiX Util extension dll to your project.

1. Under your project, right-click References
2. Select Add Reference
3. Choose the WixUtilExtension.dll and select Add