diff --git a/.arcconfig b/.arcconfig
--- a/.arcconfig
+++ b/.arcconfig
@@ -3,5 +3,6 @@
   "repository.callsign" : "G",
   "conduit_uri" : "https://reviews.llvm.org/",
   "base": "git:HEAD^",
-  "arc.land.onto.default": "main"
+  "arc.land.onto.default": "main",
+  "arc.land.onto": ["main"]
 }