Getting "'SslPolicyErrors' is not defined" when trying to validate SSL certificate in Windows XP

Question

I'm trying to validate an SSL certificate with this code:

ServicePointManager.ServerCertificateValidationCallback = New Security.RemoteCertificateValidationCallback(AddressOf CV)

Public Function CV(sender As Object, certificate As X509Certificate, chain As X509Chain, sslPolicyErrors As SslPolicyErrors) As Boolean
    Dim isOk As Boolean = True
    For Each status As X509ChainStatus In chain.ChainStatus
        Dim flag2 As Boolean = status.Status = X509ChainStatusFlags.RevocationStatusUnknown
        If Not flag2 Then
            chain.ChainPolicy.RevocationFlag = X509RevocationFlag.EntireChain
            chain.ChainPolicy.RevocationMode = X509RevocationMode.Online
            chain.ChainPolicy.UrlRetrievalTimeout = New TimeSpan(0, 1, 0)
            chain.ChainPolicy.VerificationFlags = X509VerificationFlags.AllFlags
            Dim chainIsValid As Boolean = chain.Build(CType(certificate, X509Certificate2))
            Dim flag3 As Boolean = Not chainIsValid
            If flag3 Then
                isOk = False
            End If
        End If
    Next
    Return IsOK
End Function

It works fine in Windows 10, but in Windows XP I get the following error:

'SslPolicyErrors' is not defined.

Any clues why it doesn't work in Windows XP?