  We compute the quasinormal frequencies of $d$-dimensional spherically
symmetric black holes with leading string $\alpha'$ corrections for tensorial
gravitational perturbations in the highly damped regime. We solve
perturbatively the master differential equation and we compute the monodromies
of the master perturbation variable (analytically continued to the complex
plane) in different contours, in order to obtain the quasinormal mode spectra.
We proceed analogously for the quasinormal modes of test scalar fields.
Differently than in Einstein gravity, we obtain distinct results for the two
cases.
