RULES don't apply to a newtype constructor

For some reason, RULES that involve a newtype constructor never seem to fire. The following program demonstrates the problem:

module Main where

newtype Foo a = Foo { unFoo :: a }
  deriving Show

foo :: a -> Foo a
foo = Foo

{-# RULES "rule Foo"  forall v.  Foo v = error "Foo" #-}
{-# RULES "rule foo"  forall v.  foo v = error "foo" #-}

main :: IO ()
main = do
    print (Foo ())
    print (foo ())

"rule foo" fires, but "rule Foo" doesn't. The program prints

Foo {unFoo = ()}
D: foo

Note that this doesn't seem to affect selectors, only constructors.

Trac metadata

Trac field	Value
Version	7.6.1
Type	Bug
TypeOfFailure	IncorrectResultAtRuntime
Priority	normal
Resolution	Unresolved
Component	Compiler
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