How to change plank theme?

Tried different methods, like:
creating ~/.config/plank/themes/ThemeName and setting it in config file
copying wanted theme to ~/.config/plank/themes/Default
creating simlink to folder with: ln -s .config/plank/themes/Matte .config/plank/theme
(also created folder somewhere in /usr/... I think, but now can't remember )

No change at all.

OS:
Linux Mint 13 Maya
Linux desktop 3.2.0-59-generic #90-Ubuntu SMP Tue Jan 7 22:43:51 UTC 2014 x86_64 x86_64 x86_64 GNU/Linux