Wininet.dll i kompresja http - co może być przyczyną błędu?

Witajcie,

Mam problem z funkcją InternetSetOption z biblioteki wininet.dll, którą w VBA deklaruje tak:

Private Declare Function InternetSetOption Lib "wininet.dll" Alias "InternetSetOptionA" (ByVal hInternet As Long, ByVal dwOption As Long, ByVal lpBuffer As Boolean, ByVal dwBufferLength As Integer) As Long

Jest też:

Private Const INTERNET_OPTION_HTTP_DECODING = 65

Następnie w klasie mam taką funkcję:

Private Function OpenUrl(ByVal hSession As Long, ByVal strUrl As String, Optional ByVal bRaiseError = True) As Long
    Dim hConnection As Long, lngISetOption As Long, lngBufferLength As Long, lngBuffer As Long, lngFM As Long
    Dim strContentEncodingHeader As String
    Dim intAddHeaders As Integer
    Dim strBufferFM As String * 200
    Dim boolDec As Boolean
    
    boolDec = True
    
    lngBufferLength = 1024
    'lngBuffer = 100000
    
    ' Valid session?
    If (hSession = 0) Then
        err.Raise 2345345, , "The session is not set!"
        Exit Function
    End If
    
    ' Open Url
    hConnection = InternetOpenUrl(hSession, strUrl, vbNullString, ByVal 0&, INTERNET_FLAG_EXISTING_CONNECT Or INTERNET_FLAG_RELOAD, ByVal 0&)
    
    'Gzip
    strContentEncodingHeader = "Accept-Encoding: gzip, deflate"
    intAddHeaders = HttpAddRequestHeaders(hConnection, strContentEncodingHeader, Len(strContentEncodingHeader), HTTP_ADDREQ_FLAG_REPLACE Or HTTP_ADDREQ_FLAG_ADD)
    lngISetOption = InternetSetOption(hConnection, INTERNET_OPTION_HTTP_DECODING, ByVal boolDec, Len(boolDec) + 1)

     ' Valid file?
    If (hConnection = 0) Then
        ' Error
        Call RaiseLastError
        
        ' Exit
        Exit Function
    End If

    ' Get the value
    OpenUrl = hConnection

End Function

Funkcja HttpAddRequestHeaders zwraca 1, funkcja InternetSetOption zwraca 0. Kod błędu: 87, parametr jest niepoprawny.
Co może być przyczyną błędu?

dodanie znaczników <code class="vbnet"> - furious programming