diff --git a/src/main.rs b/src/main.rs
index e06c7af..7bca39f 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -4,5 +4,5 @@ fn main() {
 
 pub enum List {
     Empty,
-    Elem(i32, List),
+    Elem(i32, Box<List>),
 }
\ No newline at end of file