diff --git a/FEM/fem_ele_std.cpp b/FEM/fem_ele_std.cpp
index a34211dd1..bd13cc4e9 100644
--- a/FEM/fem_ele_std.cpp
+++ b/FEM/fem_ele_std.cpp
@@ -1578,9 +1578,9 @@ double CFiniteElementStd::CalCoefMass()
             val = MediaProp->StorageFunction(Index, unit, pcs->m_num->ls_theta);
             double drho_dp_rho = 0.0;
             // get drho/dp/rho from material model or direct input
+            const double rho_val = FluidProp->Density();
             if (FluidProp->compressibility_model_pressure > 0)
             {
-                const double rho_val = FluidProp->Density();
                 double arg[2];
                 arg[0] = interpolate(NodalVal1);   //   p
                 arg[1] = interpolate(NodalValC1);  //   T
@@ -1588,7 +1588,7 @@ double CFiniteElementStd::CalCoefMass()
             }
             else
             {
-                drho_dp_rho = FluidProp->drho_dp;
+                drho_dp_rho = FluidProp->drho_dp / rho_val;
             }
 
             const double poro_val =
@@ -1603,7 +1603,7 @@ double CFiniteElementStd::CalCoefMass()
                 h_fem = this;
                 storage_effstress =
                     MediaProp->StorageFunctionEffStress(Index, nnodes, h_fem);
-                val *= storage_effstress;
+                val += storage_effstress;
             }
 
             // val /= time_unit_factor;
diff --git a/FEM/rf_mmp_new.cpp b/FEM/rf_mmp_new.cpp
index 6a85729e7..814f05242 100644
--- a/FEM/rf_mmp_new.cpp
+++ b/FEM/rf_mmp_new.cpp
@@ -8001,7 +8001,7 @@ double CMediumProperties::StorageFunction(long index, double* gp, double theta)
     return storage;
 }
 
-// AS:08.2012 storgae function eff stress
+// AS:08.2012 storage function of effective stress
 double CMediumProperties::StorageFunctionEffStress(long index, int nnodes,
                                                    CFiniteElementStd* h_fem)
 {