diff --git a/servo-tidy.toml b/servo-tidy.toml
index 66dd1e4cc5e..01a43ffd9c0 100644
--- a/servo-tidy.toml
+++ b/servo-tidy.toml
@@ -42,7 +42,8 @@ packages = [
   "log",
   "rand",
   "winapi",
-
+  # TODO: remove slab when #21426 lands
+  "slab",
   "syn",
   "quote",
   "proc-macro2",