1 files changed, 1 insertions, 1 deletions
diff --git a/Day13.cs b/Day13.cs
index c666c72..31425c0 100644
--- a/Day13.cs
+++ b/Day13.cs
@@ -5,7 +5,7 @@ using System.Linq;
 
 namespace aoc2019
 {
-    internal class Day13 : Day
+    internal sealed class Day13 : Day
     {
         public override int DayNumber => 13;