diff --git a/src/solvers/dgsem_p4est/dg_2d_parallel.jl b/src/solvers/dgsem_p4est/dg_2d_parallel.jl
index d76d5083573..c5c8557bfbd 100644
--- a/src/solvers/dgsem_p4est/dg_2d_parallel.jl
+++ b/src/solvers/dgsem_p4est/dg_2d_parallel.jl
@@ -5,99 +5,6 @@
 @muladd begin
 
 
-# TODO: Unify this function with the `ParallelTreeMesh` `rhs!` once mortar support has been added
-# to the `ParallelP4estMesh`
-function rhs!(du, u, t,
-              mesh::ParallelP4estMesh{2}, equations,
-              initial_condition, boundary_conditions, source_terms,
-              dg::DG, cache)
-  # Start to receive MPI data
-  @trixi_timeit timer() "start MPI receive" start_mpi_receive!(cache.mpi_cache)
-
-  # Prolong solution to MPI interfaces
-  @trixi_timeit timer() "prolong2mpiinterfaces" prolong2mpiinterfaces!(
-    cache, u, mesh, equations, dg.surface_integral, dg)
-
-  # Prolong solution to MPI mortars
-  @trixi_timeit timer() "prolong2mpimortars" prolong2mpimortars!(
-    cache, u, mesh, equations, dg.mortar, dg.surface_integral, dg)
-
-  # Start to send MPI data
-  @trixi_timeit timer() "start MPI send" start_mpi_send!(
-    cache.mpi_cache, mesh, equations, dg, cache)
-
-  # Reset du
-  @trixi_timeit timer() "reset ∂u/∂t" reset_du!(du, dg, cache)
-
-  # Calculate volume integral
-  @trixi_timeit timer() "volume integral" calc_volume_integral!(
-    du, u, mesh,
-    have_nonconservative_terms(equations), equations,
-    dg.volume_integral, dg, cache)
-
-  # Prolong solution to interfaces
-  @trixi_timeit timer() "prolong2interfaces" prolong2interfaces!(
-    cache, u, mesh, equations, dg.surface_integral, dg)
-
-  # Calculate interface fluxes
-  @trixi_timeit timer() "interface flux" calc_interface_flux!(
-    cache.elements.surface_flux_values, mesh,
-    have_nonconservative_terms(equations), equations,
-    dg.surface_integral, dg, cache)
-
-  # Prolong solution to boundaries
-  @trixi_timeit timer() "prolong2boundaries" prolong2boundaries!(
-    cache, u, mesh, equations, dg.surface_integral, dg)
-
-  # Calculate boundary fluxes
-  @trixi_timeit timer() "boundary flux" calc_boundary_flux!(
-    cache, t, boundary_conditions, mesh, equations, dg.surface_integral, dg)
-
-  # Prolong solution to mortars
-  @trixi_timeit timer() "prolong2mortars" prolong2mortars!(
-    cache, u, mesh, equations, dg.mortar, dg.surface_integral, dg)
-
-  # Calculate mortar fluxes
-  @trixi_timeit timer() "mortar flux" calc_mortar_flux!(
-    cache.elements.surface_flux_values, mesh,
-    have_nonconservative_terms(equations), equations,
-    dg.mortar, dg.surface_integral, dg, cache)
-
-  # Finish to receive MPI data
-  @trixi_timeit timer() "finish MPI receive" finish_mpi_receive!(
-    cache.mpi_cache, mesh, equations, dg, cache)
-
-  # Calculate MPI interface fluxes
-  @trixi_timeit timer() "MPI interface flux" calc_mpi_interface_flux!(
-    cache.elements.surface_flux_values, mesh,
-    have_nonconservative_terms(equations), equations,
-    dg.surface_integral, dg, cache)
-
-  # Calculate MPI mortar fluxes
-  @trixi_timeit timer() "MPI mortar flux" calc_mpi_mortar_flux!(
-    cache.elements.surface_flux_values, mesh,
-    have_nonconservative_terms(equations), equations,
-    dg.mortar, dg.surface_integral, dg, cache)
-
-  # Calculate surface integrals
-  @trixi_timeit timer() "surface integral" calc_surface_integral!(
-    du, u, mesh, equations, dg.surface_integral, dg, cache)
-
-  # Apply Jacobian from mapping to reference element
-  @trixi_timeit timer() "Jacobian" apply_jacobian!(
-    du, mesh, equations, dg, cache)
-
-  # Calculate source terms
-  @trixi_timeit timer() "source terms" calc_sources!(
-    du, u, t, source_terms, equations, dg, cache)
-
-  # Finish to send MPI data
-  @trixi_timeit timer() "finish MPI send" finish_mpi_send!(cache.mpi_cache)
-
-  return nothing
-end
-
-
 function prolong2mpiinterfaces!(cache, u,
                                 mesh::ParallelP4estMesh{2},
                                 equations, surface_integral, dg::DG)
diff --git a/src/solvers/dgsem_tree/dg_2d_parallel.jl b/src/solvers/dgsem_tree/dg_2d_parallel.jl
index d3e1d9406fc..10c198f9be1 100644
--- a/src/solvers/dgsem_tree/dg_2d_parallel.jl
+++ b/src/solvers/dgsem_tree/dg_2d_parallel.jl
@@ -443,7 +443,7 @@ end
 
 
 function rhs!(du, u, t,
-              mesh::ParallelTreeMesh{2}, equations,
+              mesh::Union{ParallelTreeMesh{2}, ParallelP4estMesh{2}}, equations,
               initial_condition, boundary_conditions, source_terms,
               dg::DG, cache)
   # Start to receive MPI data