Build failure with mtl-2.3

[sjakobi]

Building library for transient-0.7.0.0..
[1 of 8] Compiling Transient.Internals ( src/Transient/Internals.hs, dist/build/Transient/Internals.o, dist/build/Transient/Internals.dyn_o )

src/Transient/Internals.hs:363:10: error:
    Not in scope: type constructor or class ‘MonadPlus’
    |
363 | instance MonadPlus TransIO where
    |          ^^^^^^^^^

[sjakobi]

v0.6.3 seems to be affected too. Older versions of transient aren't compatible with GHC >= 8.6 and therefore have no build plans with mtl-2.3.