GHC 9.6.0.20230128 parse error on input `#.`

Summary

I get a new parse error on the 9.6.0alpha2 that I didn't have earlier.

Steps to reproduce

$ cabal install cabal-plan --constraint='cabal-plan +exe' --allow-newer="base,template-haskell,bytestring,ghc-prim"
...

src/Optics/Internal/Utils.hs:16:6: error: [GHC-58481]
    parse error on input ‘#.’
   |
16 |   , (#.)
   |      ^^

Link to the full log in cabal's CI.

Expected behavior

Builds ok as with 9.4.4 and earlier.

Environment

• GHC version used: 9.6.0.20230128

Optional:

• Operating System: all
• System Architecture: x86_64