TransformListComp weird type error

Am I missing something, or is this broken?

Prelude> :set -XTransformListComp 
Prelude> import Data.List
Prelude Data.List> [ x | x <- ['a'..'z'], then sort]

<interactive>:5:29:
    No instance for (Ord a) arising from a use of `sort'
    Possible fix:
      add (Ord a) to the context of
        a type expected by the context: [a] -> [a]
    In the expression: sort
    In a stmt of a list comprehension: then sort
    In the expression: [x | x <- ['a' .. 'z'], then sort]

Trac metadata

Trac field	Value
Version	7.6.3
Type	Bug
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	Compiler (Type checker)
Test case
Differential revisions
BlockedBy
Related
Blocking
CC
Operating system
Architecture