Output parameter of ref type long throwing Type Mismatch

[Alee02]

I have tried the following combinations

var longOuput = new Variant(0, "long")
var longOutputRef = new Variant(longOutput, "byref")

var longOuput = new Variant(0, "long")
var longOutputRef = new Variant(longOutput, "plong")

The type mismatch error occurs only when passing a reference type. Passing the following compiles fine, but the out value isn't returned.
var longOuput = new Variant(0, "long")

Here is the method signature for reference:

VARIANT GetCurrentId(
                [in] BSTR sessionID, 
                [out] long* number, 
                [out] VARIANT* error, 
                [out] VARIANT* outcome);

[Cgende]

I'm having the exact same issue. Has any one figured it out?