diff --git a/libmpdata++/solvers/detail/mpdata_rhs_vip_prs_sgs_common.hpp b/libmpdata++/solvers/detail/mpdata_rhs_vip_prs_sgs_common.hpp
index 07d15f50..b8f40e24 100644
--- a/libmpdata++/solvers/detail/mpdata_rhs_vip_prs_sgs_common.hpp
+++ b/libmpdata++/solvers/detail/mpdata_rhs_vip_prs_sgs_common.hpp
@@ -135,7 +135,8 @@ namespace libmpdataxx
                                                                                             *this->mem->G,
                                                                                             this->ijk,
                                                                                             this->dijk,
-                                                                                            real_t(2.0));
+                                                                                            real_t(2.0)); // factor of 2 because it is multiplied by 0.5 * dt in vip_rhs_apply (?)
+
           }
           else
           {