diff --git a/cosmolopy/constants.py b/cosmolopy/constants.py
index 537295e..f198650 100644
--- a/cosmolopy/constants.py
+++ b/cosmolopy/constants.py
@@ -84,6 +84,7 @@
 doc += "  sigma_T_cm: Thomson cross section in Mpc^2\n"
 sigma_T_Mpc = sigma_T_cm / (Mpc_cm ** 2.) # Mpc^2 
 
-__doc__ += "\n".join(sorted(doc.split("\n")))
+if __doc__ is not None:
+    __doc__ += "\n".join(sorted(doc.split("\n")))
 
 
diff --git a/cosmolopy/distance.py b/cosmolopy/distance.py
index f83bc95..52ec641 100644
--- a/cosmolopy/distance.py
+++ b/cosmolopy/distance.py
@@ -37,7 +37,7 @@ def set_omega_k_0(cosmo):
     """Returns the cosmo dictionary with omega_k_0 set.
     See get_omega_k_0.
     
-    Note that cosmo is not passed as \*\*cosmo for once. This function
+    Note that cosmo is not passed as \\*\\*cosmo for once. This function
     modifies the dictionary in place and returns the result.
 
     """