diff --git a/pkgs/development/python-modules/cot/default.nix b/pkgs/development/python-modules/cot/default.nix
index 89e26545d79..0c2bb961290 100644
--- a/pkgs/development/python-modules/cot/default.nix
+++ b/pkgs/development/python-modules/cot/default.nix
@@ -35,9 +35,10 @@ buildPythonPackage rec {
     "TestQCOW2"
     "TestRAW"
     "TestVMDKConversion"
+  ] ++ lib.optionals stdenv.isDarwin [
+    "test_serial_fixup_invalid_host"
   ];
 
-
   # argparse is part of the standardlib
   prePatch = ''
     substituteInPlace setup.py --replace "'argparse'," ""