diff --git a/examples/tree_2d_dgsem/elixir_navier_stokes_lid_driven_cavity.jl b/examples/tree_2d_dgsem/elixir_navier_stokes_lid_driven_cavity.jl
index bf40aaa41d..8988267561 100644
--- a/examples/tree_2d_dgsem/elixir_navier_stokes_lid_driven_cavity.jl
+++ b/examples/tree_2d_dgsem/elixir_navier_stokes_lid_driven_cavity.jl
@@ -20,7 +20,7 @@ solver = DGSEM(polydeg=3, surface_flux=flux_lax_friedrichs)
 coordinates_min = (-1.0, -1.0) # minimum coordinates (min(x), min(y))
 coordinates_max = ( 1.0,  1.0) # maximum coordinates (max(x), max(y))
 
-# Create a uniformly refined mesh with periodic boundaries
+# Create a uniformly refined mesh
 mesh = TreeMesh(coordinates_min, coordinates_max,
                 initial_refinement_level=4,
                 periodicity=false,
diff --git a/src/equations/compressible_navier_stokes_2d.jl b/src/equations/compressible_navier_stokes_2d.jl
index ebe14c4f53..f0ba41499f 100644
--- a/src/equations/compressible_navier_stokes_2d.jl
+++ b/src/equations/compressible_navier_stokes_2d.jl
@@ -1,5 +1,6 @@
 @doc raw"""
-    CompressibleNavierStokesDiffusion2D(gamma, Re, Pr, Ma_inf, equations)
+    CompressibleNavierStokesDiffusion2D(gamma, Re, Pr, Ma_inf, equations,
+                                        gradient_variables=GradientVariablesPrimitive())
 
 These equations contain the diffusion (i.e. parabolic) terms applied
 to mass, momenta, and total energy together with the advective terms from
@@ -10,6 +11,8 @@ the [`CompressibleEulerEquations2D`](@ref).
 - `Pr`: Prandtl number,
 - `Ma_inf`: free-stream Mach number
 - `equations`: instance of the [`CompressibleEulerEquations2D`](@ref)
+- `gradient_variables`: which variables the gradients are taken with respect to.
+                        Defaults to `GradientVariablesPrimitive()`.
 
 The particular form of the compressible Navier-Stokes implemented is
 ```math