Delete function with where clause on a option

Question

I have this entity (I left only relevant fields):

type UserSession = {
 Id: string
 CreatedAt: DateTime
 LastRefreshAt: DateTime option
}

and in my UserSessionRepository.fs I have this function:

member this.DeleteAbandoned (olderThen:DateTime) = 
 base.Delete (fun session -> 
 session.CreatedAt < olderThen &&
 // error: Value is not a property of UserSession
 (session.LastRefreshAt.IsNone || session.LastRefreshAt.Value < olderThen)
 )
 |> ignore

I get the error "Value is not defined as a property of UserSession" (kind of).

I changed it, trying to avoid using the .Value property:

member this.DeleteAbandoned (olderThen:DateTime) = 
 base.Delete (fun session -> 
 session.CreatedAt < olderThen &&
 // error: Object reference not set to an instance of an object
 (session.LastRefreshAt.IsNone || session.LastRefreshAt < Some(olderThen))
 )
 |> ignore

but this raises the error "Object reference not set to an instance of an object".

How to solve it?

RepoDB 10.x
.net 9