diff --git a/src/hydro_properties.c b/src/hydro_properties.c
index 5540d8c33c6263213b35697cfed2b6b5b07de2b7..f79fd832248fba8fbc55bd9fcec57e645be93159 100644
--- a/src/hydro_properties.c
+++ b/src/hydro_properties.c
@@ -123,7 +123,7 @@ void hydro_props_init(struct hydro_props *p,
 
   /* Compute the minimal energy (Note the temp. read is in internal units) */
   double u_min = phys_const->const_boltzmann_k / phys_const->const_proton_mass;
-  u_min *= p->initial_temperature;
+  u_min *= p->minimal_temperature;
   u_min *= hydro_one_over_gamma_minus_one;
 
   /* Correct for hydrogen mass fraction */
diff --git a/src/units.c b/src/units.c
index 6152d7f42f9a409bea9d057862c04d0ae9fb6a75..04e74bc4d7040ed1bde73184b125eec5d8a7fe97 100644
--- a/src/units.c
+++ b/src/units.c
@@ -50,6 +50,20 @@ void units_init_cgs(struct unit_system* us) {
   us->UnitTemperature_in_cgs = 1.;
 }
 
+/**
+ * @brief Initialises the unit_system structure with SI system
+ *
+ * @param us The unit_system to initialize
+ */
+void units_init_si(struct unit_system* us) {
+
+  us->UnitMass_in_cgs = 1000.;
+  us->UnitLength_in_cgs = 100.;
+  us->UnitTime_in_cgs = 1.;
+  us->UnitCurrent_in_cgs = 1.;
+  us->UnitTemperature_in_cgs = 1.;
+}
+
 /**
  * @brief Initialise the unit_system with values for the base units.
  *
diff --git a/src/units.h b/src/units.h
index da2c209815b07d1d5597a598ee4a61f3132e39db..08b738c5303db8b40dfbe51799d67da8df3936ce 100644
--- a/src/units.h
+++ b/src/units.h
@@ -96,6 +96,7 @@ enum unit_conversion_factor {
 };
 
 void units_init_cgs(struct unit_system*);
+void units_init_si(struct unit_system*);
 void units_init(struct unit_system* us, double U_M_in_cgs, double U_L_in_cgs,
                 double U_t_in_cgs, double U_C_in_cgs, double U_T_in_cgs);
 void units_init_from_params(struct unit_system*, struct swift_params*,