diff --git a/collects/setup/option-sig.ss b/collects/setup/option-sig.ss
index c8040aa556..2a6b1c78a4 100644
--- a/collects/setup/option-sig.ss
+++ b/collects/setup/option-sig.ss
@@ -18,6 +18,7 @@
      pause-on-errors
      force-unpacks
      specific-collections
+     specific-planet-dirs
      archives
      current-target-directory-getter
      current-target-plt-directory-getter)))