diff --git a/jax_cosmo/background.py b/jax_cosmo/background.py
index 6cec947..98f7815 100644
--- a/jax_cosmo/background.py
+++ b/jax_cosmo/background.py
@@ -1,5 +1,6 @@
 # This module implements various functions for the background COSMOLOGY
 import jax.numpy as np
+from jax import lax
 
 import jax_cosmo.constants as const
 from jax_cosmo.scipy.interpolate import interp
@@ -328,14 +329,23 @@ def transverse_comoving_distance(cosmo, a):
         \end{matrix}
         \right.
     """
-    chi = radial_comoving_distance(cosmo, a)
-    if cosmo.k < 0:  # Open universe
+    index = cosmo.k + 1
+
+    def open_universe(chi):
         return const.rh / cosmo.sqrtk * np.sinh(cosmo.sqrtk * chi / const.rh)
-    elif cosmo.k > 0:  # Closed Universe
-        return const.rh / cosmo.sqrtk * np.sin(cosmo.sqrtk * chi / const.rh)
-    else:
+
+    def flat_universe(chi):
         return chi
 
+    def close_universe(chi):
+        return const.rh / cosmo.sqrtk * np.sin(cosmo.sqrtk * chi / const.rh)
+
+    branches = (open_universe, flat_universe, close_universe)
+
+    chi = radial_comoving_distance(cosmo, a)
+
+    return lax.switch(cosmo.k + 1, branches, chi)
+
 
 def angular_diameter_distance(cosmo, a):
     r"""Angular diameter distance in [Mpc/h] for a given scale factor.
diff --git a/jax_cosmo/core.py b/jax_cosmo/core.py
index 217d13c..4ff49d6 100644
--- a/jax_cosmo/core.py
+++ b/jax_cosmo/core.py
@@ -168,13 +168,7 @@ def Omega_k(self):
 
     @property
     def k(self):
-        if self.Omega > 1.0:  # Closed universe
-            k = 1.0
-        elif self.Omega == 1.0:  # Flat universe
-            k = 0
-        elif self.Omega < 1.0:  # Open Universe
-            k = -1.0
-        return k
+        return -np.sign(self._Omega_k).astype(np.int8)
 
     @property
     def sqrtk(self):