The shape of the $Bs0\to Ds\ast -\mu +\nu \mu$ differential decay rate is obtained as a function of the hadron recoil using proton-proton collision data at a centre-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 1.7 fb$\mathrm{<mrow\; data-mjx-texclass="ORD">-1</mrow>}$ collected by the LHCb detector. The $Bs0\to Ds\ast -\mu +\nu \mu$ decay is reconstructed through the decays $Ds\ast -\to Ds-\gamma$ and $Ds-\to K-K+\pi -$. The differential decay rate is fitted with the Caprini-Lellouch-Neubert (CLN) and Boyd-Grinstein-Lebed (BGL) parametrisations of the form factors, and the relevant quantities for both are extracted.