diff --git a/browser/components/customizableui/test/browser.ini b/browser/components/customizableui/test/browser.ini
index 63631d8908da255a731055cb9415d2adac6f2f8f..5b05e094b063d161dbabecfceac9b4db3ee50482 100644
--- a/browser/components/customizableui/test/browser.ini
+++ b/browser/components/customizableui/test/browser.ini
@@ -22,8 +22,9 @@ support-files =
 [browser_913972_currentset_overflow.js]
 
 [browser_914138_widget_API_overflowable_toolbar.js]
-# Because of the specific widths, this test is fragile and won't necessarily pass on other platforms
-run-if = os == "mac"
+# Because of the specific widths, this test is fragile and has been disabled.
+# NB: it was designed for mac only, but started randomly failing there.
+skip-if = true
 
 [browser_914863_disabled_help_quit_buttons.js]
 [browser_918049_skipintoolbarset_dnd.js]