diff --git a/sim/src/lib.rs b/sim/src/lib.rs
index e602327..6cea000 100644
--- a/sim/src/lib.rs
+++ b/sim/src/lib.rs
@@ -169,6 +169,7 @@
     }
 }
 
+#[derive(Default)]
 pub struct RunStatus {
     failures: usize,
     passes: usize,