equation compiler error on "meta mutual def"

The equation compiler fails on mutual definitions that don't call each others, but only in meta lean.

--this works
mutual def f1, g1
with f1 : unit → unit
| () := ()
with g1 : unit → unit
| () := ()

--this works too
meta mutual def f2, g2
with f2 : unit → unit
| () := ()
with g2 : unit → unit
| () := f2 ()

--this doesn't:
--unexpected error, failed to generate equational lemmas in the front-end
meta mutual def f3, g3
with f3 : unit → unit
| () := ()
with g3 : unit → unit
| () := ()

The issue names no source file or test; start by reproducing the reported failure with the meta mutual def examples and trace the equation compiler path. Done means mutually defined functions that do not call each other compile successfully and their equational lemmas are generated without the front-end error.