diff --git a/src/engine.h b/src/engine.h
index 746a24b591d05d3511624349bd8e8c0670d0ab6c..126e9eddef235bae71e6b9fd173d6c7433fd5308 100644
--- a/src/engine.h
+++ b/src/engine.h
@@ -366,6 +366,7 @@ void engine_barrier(struct engine *e);
 void engine_compute_next_snapshot_time(struct engine *e);
 void engine_compute_next_stf_time(struct engine *e);
 void engine_compute_next_statistics_time(struct engine *e);
+void engine_recompute_displacement_constraint(struct engine *e);
 void engine_unskip(struct engine *e);
 void engine_drift_all(struct engine *e);
 void engine_drift_top_multipoles(struct engine *e);
diff --git a/src/velociraptor_interface.c b/src/velociraptor_interface.c
index 13a7b5f346166cceccc9aade855c2a24d554a59a..ad20c288def6f7b1a5c39e292bea3c4efb157e2f 100644
--- a/src/velociraptor_interface.c
+++ b/src/velociraptor_interface.c
@@ -57,7 +57,7 @@ void velociraptor_init(struct engine *e) {
         error("Failed to allocate VELOCIraptor conversion factors.");
 
     /* Initialize velociraptor unit system and constants */
-    units_init(e->stf_units, e->parameter_file, "VelociraptorUnitSystem");
+    units_init_from_params(e->stf_units, e->parameter_file, "VelociraptorUnitSystem");
     phys_const_init(e->stf_units, e->parameter_file, &vel_const);
 
     /* Set cosmological constants. */
@@ -82,7 +82,8 @@ void velociraptor_init(struct engine *e) {
     e->stf_conv_fac->velocitytokms = units_conversion_factor(e->internal_units, e->stf_units, UNIT_CONV_SPEED); /* 1km/s <=> 1e5cm/s */
     e->stf_conv_fac->masstosolarmass = units_conversion_factor(e->internal_units, e->stf_units, UNIT_CONV_MASS); /* 1M_sol <=> 1.99e33g */
     e->stf_conv_fac->energyperunitmass = units_conversion_factor(e->internal_units, e->stf_units, UNIT_CONV_ENERGY_PER_UNIT_MASS); /* Conversion for gravitational potential. */
-    e->stf_conv_fac->gravity = vel_const.const_newton_G; /* TODO: G = 6.67408e-8 (cgs) */
+    //e->stf_conv_fac->gravity = vel_const.const_newton_G; /* TODO: G = 6.67408e-8 (cgs) */
+    e->stf_conv_fac->gravity = 4.302051e-06; /* TODO: G = 6.67408e-8 (cgs) */
     e->stf_conv_fac->hubbleunit = e->cosmology->H; /* TODO: double check this. */
     unit_info = *e->stf_conv_fac;