In case you work with single site WordPress installation role should include ‘unfiltered_html’ capability. You can find it at the ‘All’ or ‘Core’ capabilities groups.
In case you work with multisite WordPress then ‘unfiltered_html’ capability does not active by default for security reasons. It’s possible to enable it back using special option at ‘Settings->User Role Editor->Multisite’ tab.
Thanks for your help. I discovered that ‘unfiltered_html’ was not included into the ‘Core->General’ group, but it should. This fix will be published with a next update.