diff --git a/source/blender/blenkernel/BKE_mesh_types.hh b/source/blender/blenkernel/BKE_mesh_types.hh
index a3d23169b2c..1c038a98b55 100644
--- a/source/blender/blenkernel/BKE_mesh_types.hh
+++ b/source/blender/blenkernel/BKE_mesh_types.hh
@@ -99,6 +99,7 @@ struct MeshRuntime {
 
   /** Cache for derived triangulation of the mesh, accessed with #Mesh::looptris(). */
   SharedCache<Array<MLoopTri>> looptris_cache;
+  /** Cache for triangle to original face index map, accessed with #Mesh::looptri_faces(). */
   SharedCache<Array<int>> looptri_faces_cache;
 
   /** Cache for BVH trees generated for the mesh. Defined in 'BKE_bvhutil.c' */