Access denied to /_layouts/15/ChangeSiteMasterPage.aspx

Question

I have 'Full control' permissions granted on the whole site, including Masterpage library. Everything is working fine, except the option 'Masterpage' in Site Settings(/_layouts/15/ChangeSiteMasterPage.aspx). When I click this option I get 'access denied' error, it happend before on other site, but granting access to Masterpage library solved the issue. Here access to library is granted, but I cant use the option. I workaround this by using system account, but I'm curoius what is really going on and how to solve it.