Не работает retrofit

Почему-то не работает retrofit.

MainActivity:

public class MainActivity extends AppCompatActivity {
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        String API_BASE_URL = "https://jsonplaceholder.typicode.com/";
        OkHttpClient.Builder httpClient = new OkHttpClient.Builder();
        Retrofit.Builder builder =
                new Retrofit.Builder()
                        .baseUrl(API_BASE_URL)
                        .addConverterFactory(
                                GsonConverterFactory.create()
                        );
        Retrofit retrofit =
                builder
                        .client(
                                httpClient.build()
                        )
                        .build();
        GitHubClient client =  retrofit.create(GitHubClient.class);
        Call<List<GitHubRepo>> call =
                client.reposForUser();
        call.enqueue(new Callback<List<GitHubRepo>>() {
            @Override
            public void onResponse(Call<List<GitHubRepo>> call, Response<List<GitHubRepo>> response) {
                for (GitHubRepo user : response.body()){
                    Log.i("TEST $!", String.valueOf(user.getUserId()));
                }
            }
            @Override
            public void onFailure(Call<List<GitHubRepo>> call, Throwable t) {
                // the network call was a failure
                Log.i("TEST $1: ", t.toString());
            }
        });
    }
}

GithubClient:

public interface GitHubClient {
    @GET("posts")
    Call<List<GitHubRepo>> reposForUser();
}

GitHubRepo:

public class GitHubRepo {
    private int userId;
    private int id;
    private String title;
    private String body;
    /**
     * No args constructor for use in serialization
     *
     */
    public GitHubRepo() {
    }
    /**
     *
     * @param id
     * @param body
     * @param title
     * @param userId
     */
    public GitHubRepo(int userId, int id, String title, String body) {
        super();
        this.userId = userId;
        this.id = id;
        this.title = title;
        this.body = body;
    }
    public int getUserId() {
        return userId;
    }
    public void setUserId(int userId) {
        this.userId = userId;
    }
    public int getId() {
        return id;
    }
    public void setId(int id) {
        this.id = id;
    }
    public String getTitle() {
        return title;
    }
    public void setTitle(String title) {
        this.title = title;
    }
    public String getBody() {
        return body;
    }
    public void setBody(String body) {
        this.body = body;
    }
}

P.S Всё списано с примера, изменена лишь ссылка, геттеры и сеттеры.