diff --git a/src/physical_constants.c b/src/physical_constants.c
index 7752f4d3130b7174863d520b3d4d3c6a3e8eb433..3e3c72812c552aba1204086353dc7d239a5c36f9 100644
--- a/src/physical_constants.c
+++ b/src/physical_constants.c
@@ -32,7 +32,8 @@
 /**
  * @brief Converts physical constants to the internal unit system
  *
- * Some constants can be overwritten by the YAML file values.
+ * Some constants can be overwritten by the YAML file values. If the
+ * param argument is NULL, no overwriting is done.
  *
  * @param us The current internal system of units.
  * @param params The parsed parameter file.
@@ -48,8 +49,10 @@ void phys_const_init(const struct unit_system *us, struct swift_params *params,
       const_newton_G_cgs / units_general_cgs_conversion_factor(us, dimension_G);
 
   /* Overwrite G if present in the file */
-  internal_const->const_newton_G = parser_get_opt_param_double(
-      params, "PhysicalConstants:G", internal_const->const_newton_G);
+  if (params != NULL) {
+    internal_const->const_newton_G = parser_get_opt_param_double(
+        params, "PhysicalConstants:G", internal_const->const_newton_G);
+  }
 
   const float dimension_c[5] = {0, 1, -1, 0, 0}; /* [cm s^-1] */
   internal_const->const_speed_light_c =
diff --git a/src/velociraptor_interface.c b/src/velociraptor_interface.c
index a3e836a050ef623b93b3bcd037c0e4f0d9ad4faf..cbedeebf145fd18cd9fec88c700edfa51df0377d 100644
--- a/src/velociraptor_interface.c
+++ b/src/velociraptor_interface.c
@@ -144,11 +144,10 @@ void velociraptor_init(struct engine *e) {
 #ifdef HAVE_VELOCIRAPTOR
   const ticks tic = getticks();
 
-  /* Internal SWIFT units and physical constants */
-  // const struct phys_const *swift_pc = e->physical_constants;
+  /* Internal SWIFT units */
   const struct unit_system *swift_us = e->internal_units;
 
-  /* CGS units and physical constants */
+  /* CGS units and physical constants in CGS */
   struct unit_system cgs_us;
   units_init_cgs(&cgs_us);
   struct phys_const cgs_pc;