diff --git a/unity-composite/action.yaml b/unity-composite/action.yaml
index b1053b6..3340d7d 100644
--- a/unity-composite/action.yaml
+++ b/unity-composite/action.yaml
@@ -19,6 +19,7 @@ inputs:
   buildDir:
     description: "Where the built application ends up."
     required: false
+    default: build
   cacheVolume:
     description: "Name of the volume to cache the Library folder to."
     required: true