Display attribute ignored for group definitions for pages or blocks

I created a custom group name that I wanted some of my page types to be listed under when creating new instances. This seems to work great when the name of the group is only a single word, but friendly names with spaces are ignored. Here is an example of my group definition:

        [GroupDefinitions]
        public static class ContentGroupNames
        {
            [Display(Name = "Custom Pages", Order = 70)]
            public const string CustomPages = "CustomPages";
        }

At run time the name of the group shows the constant name "CustomPages", rather than the friendly name with the space from the Display attribute. These work just fine for tabs within content, but not for page or block group names.