Warnings in check-exact break build with werror: can't run testsuite

When I try to run the testsuite with a +werror flavour, I get

utils/check-exact/ExactPrint.hs:1447:9: error: [GHC-62161] [-Wincomplete-uni-patterns, Werror=incomplete-uni-patterns]
    Pattern match(es) are non-exhaustive
    In a pattern binding:
        Patterns of type ‘EpAnn EpAnnImportDecl’ not matched: EpAnnNotUsed
     |
1447 |     let (EpAnn _anc an _cs) = ann0
     |         ^^^^^^^^^^^^^^^^^^^^^^^^^^

utils/check-exact/ExactPrint.hs:1500:9: error: [GHC-62161] [-Wincomplete-uni-patterns, Werror=incomplete-uni-patterns]
    Pattern match(es) are non-exhaustive
    In a pattern binding:
        Patterns of type ‘EpAnn EpAnnImportDecl’ not matched: EpAnnNotUsed
     |
1500 |     let (EpAnn anc' an' cs') = ann4
     |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^

utils/check-exact/ExactPrint.hs:2933:5: error: [-Wunused-matches, Werror=unused-matches]
    Defined but not used: ‘an0’
     |
2933 |     an0 <- markEpAnnLMS an lidl AnnOpen (Just "[d|")
     |     ^^^
Command failed
Build failed.

Maybe there's another ticket about this, but searching gives me a GitLab error. :(

I can make progress my changing my flavour (and with --freeze1 --freeze2 this doesn't do gratuitous rebuilding), but I would expect to be able to run the testsuite with the same flavour I can build GHC with.

Perhaps this should somehow be tested in CI?