  In the recent paper [A generalization of Taketa's theorem on M-groups,
Quaestiones Mathematicae, (2022),
https://doi.org/10.2989/16073606.2022.2081632], we give an upper bound 5/2 for
the average of non-monomial character degrees of a finite group G, denoted by
acdnm(G), which guarantees the solvability of G. Although the result is true,
the example we gave to show that the bound is sharp turns out to be incorrect.
In this paper, we find a new bound and we give an example to show that this new
bound is sharp. Indeed, we prove the solvability of G, by assuming acdnm(G) <
acdnm(SL2(5)) = 19/7.
