ubuntu 14.04 apt/aptitude autocompletion with oh-my-zsh not working

Question

I've recently begun to use zsh with oh-my-zsh in a Ubuntu 14.04 server. The problem is that autocompletions of the debian plugin do not work, i.e.

ai something<TAB>

does not autocomplete. Of course

aptitude install somethi<TAB>
apt-get install somethi<TAB>

do work correctly. The git plugin of oh-my-zsh also works without any problems whatsoever.

So I've begun to wonder if anyone has a solution to this problem.

Here are some related packages if someone needs more info:

⇒  aps zsh completion
p   bash-completion                                           - programmable completion for the bash shell
v   bash-completion:i386                                      -
p   fatrat-czshare                                            - fatrat plugin allowing download and upload to czshare
p   fatrat-czshare:i386                                       - fatrat plugin allowing download and upload to czshare
p   fizsh                                                     - Friendly Interactive ZSHell
v   git-completion                                            -
v   git-completion:i386                                       -
v   ncmpcpp-completion                                        -
v   ncmpcpp-completion:i386                                   -
i   zsh                                                       - shell with lots of features
p   zsh:i386                                                  - shell with lots of features
p   zsh-beta                                                  - transitional package to zsh
p   zsh-beta-doc                                              - transitional package to zsh-doc
i A zsh-common                                                - architecture independent files for Zsh
p   zsh-dbg                                                   - shell with lots of features (debugging symbols)
p   zsh-dbg:i386                                              - shell with lots of features (debugging symbols)
p   zsh-dev                                                   - shell with lots of features (development files)
p   zsh-dev:i386                                              - shell with lots of features (development files)
i   zsh-doc                                                   - zsh documentation - info/HTML format
p   zsh-lovers                                                - tips, tricks and examples for the zsh
p   zsh-static                                                - shell with lots of features (static link)
p   zsh-static:i386                                           - shell with lots of features (static link)
p   zshdb                                                     - debugger for Z-Shell scripts

Answer 1

Adding

setopt completealiases

after oh-my-zsh is loaded seems to fix the problem.