Unsupported Authorization Scheme: Bearer

I am trying to develop code where users can log into my web application via Yahoo. Everything is working fine and I can get the yahoo user GUID. Now the problem occurs in the last step where I want to access the user profile.

I pass the authorization key through a header request:

Authorization = "Bearer " + accessToken

      

        
        
        
      

    

and I got the following error.

{"error":{
  "@lang":"en-US",
  "@uri":"http://yahoo.com",
  "description":"Unsupported authorization scheme: \"Bearer\"",
  "detail":"Unsupported authorization scheme: \"Bearer\""
}

      

        
        
        
      

    

I also tried converting accessToken to base 64 string, but it didn't work either.