1 files changed, 1 insertions, 1 deletions
diff --git a/Day15.cs b/Day15.cs
index 96e6f90..b68d251 100644
--- a/Day15.cs
+++ b/Day15.cs
@@ -4,7 +4,7 @@ using System.Linq;
 
 namespace aoc2019
 {
-    internal class Day15 : Day
+    internal sealed class Day15 : Day
     {
         public override int DayNumber => 15;