diff --git a/src/solvers/dgsem_p4est/dg_3d_parabolic.jl b/src/solvers/dgsem_p4est/dg_3d_parabolic.jl
index 99c542049e4..0bb97c7af02 100644
--- a/src/solvers/dgsem_p4est/dg_3d_parabolic.jl
+++ b/src/solvers/dgsem_p4est/dg_3d_parabolic.jl
@@ -879,7 +879,7 @@ function calc_mortar_flux_divergence!(surface_flux_values,
         k_small_start, k_small_step_i, k_small_step_j = index_to_start_step_3d(small_indices[3],
                                                                                index_range)
 
-        for position in 1:4
+        for position in 1:4 # Loop over small elements
             i_small = i_small_start
             j_small = j_small_start
             k_small = k_small_start