diff --git a/packages/darwin_app/Makefile b/packages/darwin_app/Makefile
index 2a6e07ae034fe26b884711d2d9432157ee044999..2b04949fa3836ae1b8fe2f26b0be6bb8a8a9b094 100644
--- a/packages/darwin_app/Makefile
+++ b/packages/darwin_app/Makefile
@@ -105,6 +105,7 @@ extended_app_install:
 # build a standalone nw.js app
 darwin_app_wrapper: Info.plist
 # nwjs.app
+	rm -rf "$(BUILD_BASE)"
 	install -d "$(BUILD_BASE)"
 	rsync -ax $(cvs_root_dir)/pd/nw/nw/nwjs.app/ $(BUILD_BASE)/$(PD_APP_NAME).app/
 # set up app wrapper