key bindings should not be restricted to alphanumeric

I would like to use a key binding that includes [ and ] but these are reported as being invalid. I tried { and } as well, but these were also invalid. Here is the key binding in question, and the console log:

{ "keys": ["ctrl+super+alt+]"], "command": "insert_time" },

Unknown key ]
Unable to parse binding {command: insert_time, keys: [ctrl+super+alt+]]}

This binding works when I change ] to an alpha key like n.