Global.asax error - Request not available in this context

I get the error with this code...

Code:

Sub Application_Start(ByVal sender As Object, ByVal e As EventArgs)
        ' Code that runs on application startup
        If HttpContext.Current.Request.IsSecureConnection.Equals(False) Then
            Response.Redirect("https://" + Request.ServerVariables("HTTP_HOST") + HttpContext.Current.Request.RawUrl)
        End If
    End Sub

how can I fix this? I've tried to reload the page. the site works when I comment out the code, but I get the error when I try to use it.