  It is shown that in the presence of a nonvanishing cosmological constant,
Strominger's infinite-dimensional $\mathrm{w_{1+\infty}}$ algebra of soft
graviton symmetries is modified in a simple way. The deformed algebra contains
a subalgebra generating $ SO(1,4)$ or $SO(2,3)$ symmetry groups of
$\text{dS}_4$ or $\text{AdS}_4$, depending on the sign of the cosmological
constant. The transformation properties of soft gauge symmetry currents under
the deformed $\mathrm{w_{1+\infty}}$ are also discussed.
