diff --git a/action.yml b/action.yml
index a678a1f..1960907 100644
--- a/action.yml
+++ b/action.yml
@@ -15,7 +15,6 @@ inputs:
   source-branch:
     description: The branch of `magic-nix-cache` to use. Conflicts with all other `source-*` options.
     required: false
-    default: main
   source-pr:
     description: The PR of `magic-nix-cache` to use. Conflicts with all other `source-*` options.
     required: false