Linux Mate: keepassxc icon is stretched disproportionally. How to fix?

I am running a Linux Mint with Mate window manager on board. For some reason, some of the icons in the tray are resized to fit the panel height, others are not. Weird thing is happening to the keepassxc icon that is rendered disproportionally stretched - an oval-shaped. Can anybody give a suggestion how to tweak it so the icon shape is proper (be it small or big, but circle)?