diff --git a/src/cosmology.c b/src/cosmology.c
index b696d1f8740823d5a808c721c2f756198507279d..3c8954d352df03ba1e7796e84e3bd328af022899 100644
--- a/src/cosmology.c
+++ b/src/cosmology.c
@@ -193,6 +193,9 @@ void cosmology_update(struct cosmology *c, const struct phys_const *phys_const,
   /* Mean density */
   c->mean_density = c->critical_density_0 * c->a3_inv;
 
+  /* Mean baryonic density */
+  c->mean_density_Omega_b = c->mean_density * c->Omega_b;
+
   /* Time-step conversion factor */
   c->time_step_factor = c->H;
 
@@ -587,6 +590,7 @@ void cosmology_init_no_cosmo(struct cosmology *c) {
   c->critical_density = 0.;
   c->critical_density_0 = 0.;
   c->mean_density = 0.;
+  c->mean_density_Omega_b = 0;
 
   c->time_step_factor = 1.;
 
diff --git a/src/cosmology.h b/src/cosmology.h
index b1af210f143417adcfff840e5302fa1bcd54f0b8..7b50a738db72b9a82ad1bbb67fc68622dd6208e8 100644
--- a/src/cosmology.h
+++ b/src/cosmology.h
@@ -81,6 +81,9 @@ struct cosmology {
   /*! The mean density at the current redshift (in internal physical units) */
   double mean_density;
 
+  /*! The mean baryonic density at the current redshift (in internal physical units) */
+  double mean_density_Omega_b;
+
   /*! Conversion factor from internal time-step size to cosmological step */
   double time_step_factor;