diff --git a/ProcessLib/RichardsComponentTransport/RichardsComponentTransportFEM.h b/ProcessLib/RichardsComponentTransport/RichardsComponentTransportFEM.h
index 1fd44aaca6d07a47e65f363f2e0455ec8d06c52b..f4b1cab4453035099aa15907b08ee9ca31e0ed96 100644
--- a/ProcessLib/RichardsComponentTransport/RichardsComponentTransportFEM.h
+++ b/ProcessLib/RichardsComponentTransport/RichardsComponentTransportFEM.h
@@ -306,7 +306,7 @@ public:
                              ip_data.mass_operator;
 
             if (_process_data.has_gravity)
-                Bp += w * density * dNdx.transpose() * K_over_mu * b;
+                Bp += w * density * dNdx.transpose() * K * b * (k_rel/mu);
             /* with Oberbeck-Boussing assumption density difference only exists
              * in buoyancy effects */
         }