Declaration is duplicated in the Outline?

[mysecondnameisdanger]

Declaration is duplicated in the outline on the pdf reader (evince in my case)

% !TEX root = ../my-thesis.tex
%
%************************************************
% Declaration
%************************************************
\pdfbookmark[0]{Declaration}{Declaration}
\addchap{Declaration}

To fix this we need to comment out line number 6 in declaration.tex or maybe just delete it?