Could not load file or assembly 'Microsoft.VisualStudio.Shell, Version=' on import


I have Visual Studio Professional 2012 (Update 5) and StudioShell 1.6.5 installed (full install, not the nuget package)

When I try to import the StudioShell module in a standard Powershell host, I get the following:
PS C:\Projects\> import-module StudioShell
import-module : Could not load file or assembly 'Microsoft.VisualStudio.Shell, Version=, Culture=neutral,
PublicKeyToken=b03f5f7f11d50a3a' or one of its dependencies. The system cannot find the file specified.
At line:1 char:1
+ import-module StudioShell
+ ~~~~~~~~~~~~~~~~~~~~~~~~~
    + CategoryInfo          : InvalidOperation: (:) [Import-Module], FileNotFoundException
    + FullyQualifiedErrorId : ProviderStartException,Microsoft.PowerShell.Commands.ImportModuleCommand

DEBUG: connecting to StudioShell add in instance
Unable to find type [CodeOwls.StudioShell.Connect].
At C:\Program Files (x86)\Code Owls LLC\StudioShell\start-studioshell.psm1:76 char:1
+ [CodeOwls.StudioShell.Connect]::RegisterRunspace( $host.runspace );
+ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    + CategoryInfo          : InvalidOperation: (CodeOwls.StudioShell.Connect:TypeName) [], RuntimeException
    + FullyQualifiedErrorId : TypeNotFound
I've tried a repair on StudioShell's installation. I'm not sure whether SS is looking for something it shouldn't, or whether something that ought to be registered in the GAC is not. Any insight?