diff --git a/pkgs/development/python-modules/nbconvert/default.nix b/pkgs/development/python-modules/nbconvert/default.nix
index 69828b2b18f..2f0090b5967 100644
--- a/pkgs/development/python-modules/nbconvert/default.nix
+++ b/pkgs/development/python-modules/nbconvert/default.nix
@@ -44,6 +44,9 @@ buildPythonPackage rec {
     HOME=$(mktemp -d) py.test -v --ignore="nbconvert/preprocessors/tests/test_execute.py"
   '';
 
+  # Some of the tests use localhost networking.
+  __darwinAllowLocalNetworking = true;
+
   meta = {
     description = "Converting Jupyter Notebooks";
     homepage = https://jupyter.org/;