1 files changed, 1 insertions, 1 deletions
diff --git a/Day12.cs b/Day12.cs
index 663742d..efb380a 100644
--- a/Day12.cs
+++ b/Day12.cs
@@ -5,7 +5,7 @@ using System.Linq;
 
 namespace aoc2019
 {
-    internal class Day12 : Day
+    internal sealed class Day12 : Day
     {
         public override int DayNumber => 12;