diff --git a/pkgs/development/python-modules/curio/default.nix b/pkgs/development/python-modules/curio/default.nix
index 1a0f4e2d9fe7..7a66e4796648 100644
--- a/pkgs/development/python-modules/curio/default.nix
+++ b/pkgs/development/python-modules/curio/default.nix
@@ -26,9 +26,10 @@ buildPythonPackage rec {
 
   disabledTests = [
      "test_aside_basic" # times out
+     "test_write_timeout" # flaky, does not always time out
      "test_aside_cancel" # fails because modifies PYTHONPATH and cant find pytest
      "test_ssl_outgoing" # touches network
-   ] ++ lib.optionals (stdenv.isDarwin) [
+   ] ++ lib.optionals stdenv.isDarwin [
      "test_unix_echo" # socket bind error on hydra when built with other packages
      "test_unix_ssl_server" # socket bind error on hydra when built with other packages
    ];