Whats wrong with this defcustom?

[Thorsten Jolitz]

Hi List, 

I'm probably overlooking the obvious, but what is wrong with this
defcustom:

,----
| (defcustom org-x-style 'notes
|   "Possible styles for diagrams."
|   :group 'org-x
|   :type '(choice (const :tag "Sync-bars" 'sync-bars)
|                (const :tag "Partitions" 'partitions)
|                (const :tag "Notes" 'notes)))
`----

why do I get the (mismatch) note but no choices?

,----
| Hide org-x-style: 'notes
|    [ State ]: STANDARD. (mismatch)
|    Possible styles for diagrams.
| Groups: [Org X]
`----

Thanks in advance for any hint.

-- 
cheers,
Thorsten