diff --git a/src/main.rs b/src/main.rs
index 3fd89d8..8d29ea8 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -24,7 +24,7 @@ struct Args {
     before: String,
 
     /// the generation we are switching to
-    #[argh(positional)]
+    #[argh(positional, default = "String::from(\"/run/current-system/\")")]
     after: String,
 }