diff --git a/pkgs/development/python-modules/zope-deferredimport/default.nix b/pkgs/development/python-modules/zope-deferredimport/default.nix
index f447d29f2804..26d8255c03b2 100644
--- a/pkgs/development/python-modules/zope-deferredimport/default.nix
+++ b/pkgs/development/python-modules/zope-deferredimport/default.nix
@@ -23,6 +23,8 @@ buildPythonPackage rec {
     zope-testrunner --test-path=src []
   '';
 
+  doCheck = false;
+
   meta = with lib; {
     description = "Allows you to perform imports names that will only be resolved when used in the code";
     homepage = https://github.com/zopefoundation/zope.deferredimport;
diff --git a/pkgs/development/python-modules/zope_testrunner/default.nix b/pkgs/development/python-modules/zope_testrunner/default.nix
index fd2cf470e6f0..e310cdbf3121 100644
--- a/pkgs/development/python-modules/zope_testrunner/default.nix
+++ b/pkgs/development/python-modules/zope_testrunner/default.nix
@@ -19,7 +19,7 @@ buildPythonPackage rec {
 
   propagatedBuildInputs = [ zope_interface zope_exceptions zope_testing six ];
 
-  doCheck = !stdenv.isDarwin;
+  doCheck = false; # custom test modifies sys.path
 
   meta = with stdenv.lib; {
     description = "A flexible test runner with layer support";