--- a/testing/mochitest/runtests.py
+++ b/testing/mochitest/runtests.py
@@ -2211,18 +2211,18 @@ toolbar#nav-bar {
             # 1325148, but it couldn't land until all the regressions were also fixed or
             # backed out. Rather than waiting and risking new regressions, in the meantime
             # this code will selectively disable leak checking on flavors/directories where
             # known regressions exist. At least this way we can prevent further damage while
             # they get fixed.
 
             info = mozinfo.info
             skip_leak_conditions = [
-                (options.flavor in ('browser', 'chrome', 'plain') and d.startswith('toolkit/components/extensions/test/mochitest'), 'bug 1325158'),  # noqa
-                (info['debug'] and options.flavor == 'browser' and d.startswith('browser/components/extensions/test/browser'), 'bug 1325141'),  # noqa
+                (info['debug'] and options.flavor == 'plain' and d.startswith('toolkit/components/extensions/test/mochitest') and info['os'] == 'mac', 'bug 1326456'),  # noqa
+                (info['debug'] and options.flavor == 'browser' and d.startswith('browser/components/extensions/test/browser') and info['os'] == 'mac', 'bug 1325141'),  # noqa
                 (info['debug'] and options.flavor == 'plain' and d == 'dom/animation/test/css-animations', 'bug 1325277'),  # noqa
                 (info['debug'] and options.flavor == 'plain' and d == 'dom/tests/mochitest/gamepad' and info['os'] == 'win', 'bug 1324592'),  # noqa
                 (info['debug'] and options.flavor == 'plain' and d == 'toolkit/components/prompts/test' and info['os'] == 'mac', 'bug 1325275'),  # noqa
                 (info['debug'] and options.flavor == 'plain' and d == 'tests/dom/xhr/tests', 'bug 1325438'),  # noqa
             ]
 
             for condition, reason in skip_leak_conditions:
                 if condition: