Argument not optional - Dictionary and Classes

[ValentinBIA]

Hello everyone! I'm fairly new to VBA, and I'm currently experimenting with Classes and Dictionaries.
However I encountered a problem, that for once, I was not able to solve using the infinite amount of ressources available on the internet.

Whenever I run my macro, I get the "argument not optional" compile error.
It highlights the 4th line of the below code in yellow and the "pParts" on the 5th line in blue.

I think that the error might be due to the fact that contrary to strings or longs, I cannot use Value for a scripting.dictionary. However, I don't know what to use instead.
Does someone know the answer to my question?

Public Property Get Parts() As Scripting.Dictionary
    Parts = pParts
End Property
Public Property Let Parts(Value As Scripting.Dictionary)
    pParts = Value
End Property

Thank you very much!

Best,

Valentin