diff --git a/pkgs/development/python-modules/h11/default.nix b/pkgs/development/python-modules/h11/default.nix
index f77c267d792c..361ac0c59d13 100644
--- a/pkgs/development/python-modules/h11/default.nix
+++ b/pkgs/development/python-modules/h11/default.nix
@@ -23,6 +23,9 @@ buildPythonPackage rec {
     py.test
   '';
 
+  # Some of the tests use localhost networking.
+  __darwinAllowLocalNetworking = true;
+
   meta = with lib; {
     description = "Pure-Python, bring-your-own-I/O implementation of HTTP/1.1";
     license = licenses.mit;