Exact match installing Mono.Cecil nuget package

In VS2013.4, when I try to add Mono.Cecil nuget package to fsharp project:

PM> Install-Package Mono.Cecil
Installing 'Mono.Cecil 0.9.5.4'.
Successfully installed 'Mono.Cecil 0.9.5.4'.
Adding 'Mono.Cecil 0.9.5.4' to Ying.Unit.
No exact match found for removing reference 'Mono.Cecil.Mdb'. Trying case-insensitive search...
Failed to find match for removing reference 'Mono.Cecil.Mdb'.
No exact match found for removing reference 'Mono.Cecil.Pdb'. Trying case-insensitive search...
Failed to find match for removing reference 'Mono.Cecil.Pdb'.
No exact match found for removing reference 'Mono.Cecil.Rocks'. Trying case-insensitive search...
Failed to find match for removing reference 'Mono.Cecil.Rocks'.
Uninstalling 'Mono.Cecil 0.9.5.4'.
Successfully uninstalled 'Mono.Cecil 0.9.5.4'.
Install failed. Rolling back...
Install-Package : Failed to add reference to 'Mono.Cecil.Mdb'.
At line:1 char:1
+ Install-Package Mono.Cecil
+ ~~~~~~~~~~~~~~~~~~~~~~~~~~
    + CategoryInfo          : NotSpecified: (:) [Install-Package], InvalidOperationException
    + FullyQualifiedErrorId : NuGetCmdletUnhandledException,NuGet.PowerShell.Commands.InstallPackageCommand

      

        
        
        
      

    

My project targets .NET 4.5 with an F # 3.1 (4.3.1.0) runtime.

Any thoughts?

thank

Vianne